preparation surface textbook andmasking (ref02e)
TRANSCRIPT
SurfacePreparationand�Masking
(REF02e)
Textbook
Version:�4.2
©�2002�-�2014�Inter-Industry�Conference�On�Auto�Collision�Repair
REF02e-STMAN1-E
Surface�Preparation�and�Masking�(REF02e)Textbook
Table�of�Contents 3
Contents
Module�1�-�Finish�Identification...............................................................................................7Finishes�And�Refinish�Materials............................................................................................ 7Developing�A�Refinishing�Plan........................................................................................... 13Module�Wrap�Up............................................................................................................... 18
Module�2�-�Finish�Protection�And�Removal........................................................................... 21Masking�Or�Removing�Parts................................................................................................21Finish�Removal................................................................................................................... 30Module�Wrap�Up............................................................................................................... 33
Module�3�-�Spray�Gun�Technique.......................................................................................... 37Spray�Gun�Setup.................................................................................................................37Spray�Gun�Application�Techniques.....................................................................................39Module�Wrap�Up............................................................................................................... 44
Module�4�-�Substrate�Preparation...........................................................................................47Preparing�Substrates............................................................................................................47Plastics................................................................................................................................51Bare�And�Repaired�Steel.....................................................................................................52Bare�And�Repaired�Aluminum�Parts....................................................................................53Making�A�Sprayout�Panel....................................................................................................54Specialty�Spray�Areas..........................................................................................................55Module�Wrap�Up............................................................................................................... 57
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Finishes�And�Refinish�Materials
Learning�objectives�for�this�moduleinclude:
• identifying�the�types�of�personalprotection�required�for�refinishing.
• identifying�the�types�of�refinishprimers.
• identifying�the�types�of�OEMfinishes.
Wearing�the�proper�personal�protection�equipmentprevents�hazardous�materials�from�entering�thebody.
Working�with�refinish�materials�requiresparticular�attention�to�personal�safety.Refinish�materials�contain�chemicals,�thatwhen handled�during�mixing�or�atomizedthrough�the�application�process,�becomea�personal�safety�issue.�Whether�inhaledor�spilled�on�the�skin,�hazardous�materialscan�enter�the�body�and�cause�serioushealth�issues.
For�this�reason,�personal�protectionequipment�(PPE)�is�required�whenworking�with�refinishing�materials.�Thisincludes:
• eye�protection.�To�protect�eyes,wear�safety�goggles�or�a�supplied-air�respirator�when�refinishing.It�is�also�important�to�know�thelocation�of�the�eye�wash�station�incase�of�an�emergency.
• hand�protection,�such�aschemical-resistant�gloves.�Weargloves�made�of�butyl�rubber,neoprene,�or�nitrile�rubber�forthe�best�protection�from�refinishmaterials.
• clothing�(paint�suit).�Paint�suits�aredesigned�to�prevent�exposure�tomaterial�overspray�or�isocyanates.There�are�a�variety�of�materialsthat�paint�suits�are�made�of�thatprevent�exposure�to�refinishmaterials.�These�suits�may�bemade�of�cotton,�nylon,�or�a�papermaterial.�Paint�suits�are�designedto�be�disposable�and�may�have�alimited�effective�life.
• air-purifiying�respirator�orsupplied-air�respirator.�If�usinga�cartridge�respirator,�be�sureto�change�out�the�cartridges�ona�scheduled�basis�and�that�theproper�cartridges�are�being�usedfor�the�material�being�sprayed.
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These�are�examples�of�primers,�basecoats,�andclearcoats�that�are�made�by�Glasurit.
Types�of�materials�used�for�refinishinginclude:
• additives,�such�as�adhesionpromoters�or�blending�additives.Adhesion�promoters are�typicallyused�on�plastic�to�help�theadhesion�of�refinish�materials.�Ablending�additive�is�used�beforerefinishing�a�spot�repair�thatrequires�blending�into�the�panel.
• corrosion-resistant�primers.�Inaddition�to�providing�corrosionresistance,�these�primers�mayalso�be�used�to�aid�in�materialadhesion.
• primer-surfacers,�which�are�usedto�fill�very�minor�scratches�and�aidin�leveling�a�surface.
• primer-sealers,�which�are�used�toaid�in�adhesion�of�the�topcoat�tothe�primer-surfacer�and�help�withcolor�hold-out.
• basecoat�and�clearcoat.�Somevehicle�maker�finishes�include�atranslucent�pearl�or�translucentcolored�midcoat.�This�is�calleda�tri-coat�finish.�Some�customfinishes�include�multiple�layers�oftinted�clearcoat,�however,�for�the
purposes�of�this�course,�the�topicswill�remain�related�to�factoryfinishes.
These�are�examples�of�metal�cleaner�and�conversioncoating�used�for�bare�metal�corrosion�protection.
Metal�cleaners�and�conversion�coatingsare�used�on�exposed�metal.�The�metalcleaner�is:
• a�phosphoric�acid-based�cleaner. • used�to�deep�clean a�metal
surface.
Following�the�application�of�the�cleaner,a�phosphoric�acid-based�conditioner�isused.�This�places�an�even�layer�of�zincphosphate�on�either�galvanized�or�baresteel�surfaces.�Galvanizing�is�the�processof�applying�a�zinc�coating�to�sheet�steelduring�the�steel�manufacturing�process.
Using�these�preparation�steps�andmaterials�helps�replace�the�corrosionprotection�material�that�may�be�lostby�removal�of�the�galvanized�coating.Conversion�coatings:
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• chemically�adhere�to�the�basematerial.
• aid�in�corrosion�protection.
Using�metal�cleaner�and�conversioncoating�is�a�process�most�often�doneon�restorations�projects�rather�than�inproduction�repair�facilities.
There�are�several�product�makers�for�expoxy�primer.
This�epoxy�primer�is�being�applied�over�body�filler.
An�epoxy�primer:
• may�be�a�one-�or�two-partmaterial.�Two-part�primers�usea�catalyst�to�cure�rather�thanevaporation�of�solvent.�One-partepoxy�primers,�or�epoxy�esters,
are�not�prominent�in�the�collisionindustry.
• may�be�a�two-part�aerosol.�Two-part�aerosols�have�a�limited�shelflife�once�tapped.
• may�require�that�a�metalconditioner�and�conversioncoating�be�applied�first.
• may�adhere�best�to�nongalvanizedmetal.
• may�be�recommended�underplastic�body�filler�by�some�vehiclemakers.�Toyota�recommends�thispractice.�This�is�because�whenfillers�are�applied�over�the�typeof�zinc�coating�process�used�byToyota,�the�filler�material�will�notadhere�adequately.�Blistering�orpeeling�may�result.
• is�not�intended�for�filling�minorsurface�imperfections.
These�are�examples�of�self-etching�primers�made�byseveral�different�manufacturers
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This�application�stick�allows�self-etching�primer�to�beapplied�to�bare�metal�only.
Self-etching�primers:
• which�contain�acid,�are�designedto�chemically�etch�into�the�baremetal�surface�they�are�applied�to.
• offer�a�good�corrosion-resistantsurface.
• can�provide�good�topcoatadhesion.
Wash�primers�are�a�form�of�self-etchingprimer�that�are�even�thinner�than�self-etching�primers�when�applied.
A�spray�gun�with�a�plastic�or�lined�paintcup�is�recommended�when�using�self-etching�primers.�This�will�prevent�a�metalcup�from�becoming�etched�and�damagedfrom�the�acid�in�the�primer.
Axalta�offers�a�primer-surfacer�which�can�be�appliedwith�a�roller.
Primer-surfacer:
• has�high-build�characteristics,allowing�it�to�be�used�to�level�outthe�surface.
• requires�sanding�after�application.• helps�hide�contour�mapping.
Contour�mapping�is�the�outliningof�body�filler�that�has�notbeen�properly�prepared�or�theinadequate�hiding�of�surfacedefects,�such�as�a�hard�tape�line�ora�poorly�prepared�featheredge�thathas�shrunk�or�swelled.
• can�be�waterborne.�PPG�hasa�waterborne�primer-surfacer,EPW115�and�P950-5505,�thatrequires�no�etch�primer�and�canbe�applied�over�bare�metal.�Theyare�also�one�part,�so�there�areno�pot�life�issues.�Waterbornedirect-to-metal�contains�corrosioninhibitors,�which�are�required�forwaterborne�products�to�be�applieddirectly�to�bare�metal.
Sherwin-Williams�has�a�direct-to-metalprimer-surfacer,�but�only�for�use�on�a�spotrepair�that�is�5"�in�diameter�or�smaller.�A
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repair�greater�than�that�diameter�must�firsthave�self-etching�primer�applied�beforethe�primer-surfacer.
This�sealer�is�being�applied�over�a�scuffed�hood.
Sealers:
• are�applied�over�primer,�primer-surfacer,�properly�prepared�E-coat,or�sanded�basecoat�/�clearcoat.Sealer�is�applied�before�the�coloror�basecoat.
• provide�adhesion�for�the�basecoatand�protect�the�primer�frombasecoat�solvents.�Sealerapplication�can�reduce�the�risk�ofsandscratch�swelling,�shrinkage,and�solvent�absorption.
• have�limited�film-buildcharacteristics�and�are�notdesigned�to�fill�surfaceimperfections.
• are�generally�not�sanded,�butnibs�or�imperfections�can�bescuffed�and�another�coat�of�sealerapplied.�Sanding�is�required�ifsealer�is�not�topcoated�for�anextended�period�of�time.�Checkthe�paint�maker�specifications�forrecommendations.
• may�be�tinted�or�tintable�for�betterhiding.�A�variety�of�shades�may�beavailable�to�reduce�the�number�oftopcoats�that�are�required.
• provide�color�holdout�to�preventprimer�spots�from�showingthrough�and�for�overall�hiding�anduniformity.
The�difference�between�a�sealer�and�aprimer-sealer�is�that�a�primer-sealer�canbe�applied�over�bare�metal.�Sealer�are�notdesigned�for�bare�metal�but�will�protectminor�scratches�that�go�through�to�baremetal.
Some�products,�such�as�these,�are�waterborneprimer-surfacers�that�offer�corrosion�protection�overbare�steel.
Direct-to-metal�primers:
• are�a�two-part�material�that�canbe�applied�directly�to�a�bare�metalsurface.
• work�similar�to�a�self-etching�orepoxy�primer.
Some�may�be�used�as�a�sealer�or�asurfacer,�depending�on�how�it�is�reduced.There�is�no�need�to�apply�a�separateprimer�and�sealer�because�it�works�asboth.
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The�following�paint�makers�have�a�primerthat�may�either�be�applied�to�a�bare�metalsurface�or�to�an�E-coated�surface:
• Axalta• PPG• Sherwin�Williams• Akzo�Nobel• Glasurit
All�of�the�products�are�referred�to�asdirect-to-metal�primers.
This�adhesion�promoter�is�being�applied�to�bareplastic�before�priming.
Adhesion�promoters�are�generally:
• used�on�bare,�sanded plastic�parts.• required�on�polyolefin�plastic.
OEM�finishes�can�be�made�up�of�multiple�layers.
The�different�types�of�OEM�finishes�thatmay�be�used�on�a�vehicle�include:
• single-stage,�which�is�rarely�usedin�vehicle�production�anymore.
• basecoat�/�clearcoat.�This�is�themost�common�finish�offered�byvehicle�makers.
• tri-coat,�which�includes�a�midcoatbetween�the�basecoat�andclearcoat.
A�basecoat�/�clearcoat�finish�is�built�over�the�top�ofmetal�treatment,�E-coat,�and�primer.
Basecoats�are:
• the�color�coat.
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• not�designed�to�provide�a�glossappearance.
• followed�by�an�application�ofclearcoat.
• either�a�solid�color,�metallic,�ormica.
Clearcoats�are�used�to:
• provide�basecoat�protectionagainst�the�sun's�ultraviolet�(UV)rays.�This�protection�keeps�thebasecoat�from�delaminating,peeling,�and�turning�hazy.
• protect�against�abrasions�anddamage�to�the�basecoat.
• enhance�the�appearance�and�colorof�the�basecoat.
A�tri-coat�finish�has�a�midcoat�sandwiched�betweenthe�basecoat�and�the�clearcoat�that�may�consist�ofmicas�or�pearls.
A�tri-coat�is�the�addition�of�a�midcoatbetween�the�basecoat�and�the�clearcoat.Midcoats�are�applied�to�help�accent�thecolor�appearance�of�a�finish.�The�midcoatmay�consist�of�a�translucent-coloredbasecoat,�which�typically�containsmica. Mica�is�the�additive�used�to�create
pearl�coatings.�It�adds�a�metallic�sheen�tothe�appearance�of�a�finish.
Developing�A�Refinishing�Plan
The�paint�code�for�this�vehicle�is�located�on�the�doorshell.
When�determining�the�type�of�finishsystem�used�on�a�vehicle,�the�paint�codeneeds�to�be�located.�Finish�identificationneeds�to�be�understood�to�allow�for�aproper�color�match.
Paint�code�labels�may�be�located:
• on�door�pillars.• on�the�radiator�core�support.• on�strut�towers.• on�the�floor�pan.• under�the�passenger�or�driver�seat.• inside�the�trunk.• inside�the�glove�box.• inside�the�center�console.
Depending�on�the�refinish�system�used,some�paint�makers�publish�books�thatshow�an�image�of�the�paint�label�andwhere�the�paint�code�is�located.�Somepaint�makers�list,�per�vehicle,�where�thepaint�code�label�might�be�located�anddisplays�a�variety�of�paint�chips�with�the
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OEM�paint�code�listed.�This�allows�therefinisher�to�compare�colors�and�also�havethe�paint�code.
It�needs�to�be�determined�if�this�scratch�requires�lightsanding�for�prep,�or�if�it�needs�to�be�sanded�to�baremetal.
Before�refinishing�can�begin,�thereneeds�to�be�a�plan�developed�about�howthe�refinishing�will�be�performed.�Therefinishing�plan�should�include:
• the�type�and�size�of�damage�thatoccurred.
• determining�whether�or�notthe�damage�can�be�correctedby�detailing�or�if�refinishing�isneeded.
• if�the�existing�finish�will�needto�be�removed�partially�orcompletely.
• whether�panel�edging�will�beneeded.
• determining�whether�or�notthe�adjacent�panels�need�to�beblended.
As�a�refinishing�plan�is�developed,�theremust�be�a�decision�made�regardingwhether�parts�of�a�vehicle�should�beremoved�or�masked.�Is�it�best�to�remove
trim�or�glass�or is�masking�the�areas�thebest�decision?�Sometimes�there�may�bepaint�maker�or�OEM�warranty�concernsthat�mandate�how�a�vehicle�part�isprotected.
This�sealer�was�applied�over�an�E-coatedreplacement�part.
When�developing�a�refinishing�plan,�it�isalso�important�to�identify�the�substrate.Substrates�are�any�surface�that�offers�asound�foundation�for�the�application�ofrefinish�materials.�Examples�include:
• the�original�OEM�finish.• E-coat.• primer.• a�refinish.
Substrates�can�also�be�base�material�suchas:
• steel.• aluminum.• plastic,�both�rigid�and�flexible.
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Cleaning�with�soap�and�water�first�helps�removesurface�contaminants.
When�cleaning�a�surface�for�inspection,always�start�with�mild�water-basedproducts�and�work�into�stronger�solvent-based�products�that�will�not�affect�thebase�material�or�substrate.
As�surface�cleaning�begins,�keep�thesurface�wet.�This�allows�the�debris�to�floatto�the�surface�and�not�be�re-embeddedinto�the�finish.�Use�one�towel�for�washingthe�surface�and�a�separate�towel�forwiping�off�the�surface.
Inspecting�a�featheredge�will�reveal�the�number�offinish�coats�applied�to�an�area.
Featheredging�is�done�to�ensure�a�smoothtransition�from�the�repair�area�to�theundamaged�area.�When�inspecting�thefeatheredge,�look�for:
• whether�the�finish�is�basecoat�/clearcoat�or�a�tri-coat�system.
• the�amount�and�number�of�finishcoats�applied.
• whether�there�is�good�finishadhesion.
• if�there�is�acceptable�filmthickness.
A�film�thickness�reading�of�3.82�mils�should�allowadditional�coatings�to�be�applied�without�anyproblems.
Paint�makers�have�limits�as�to�themaximum�amount�of�refinish�material�thatshould�be�applied.�This�thickness�is�thetotal�amount�of�material�on�a�surface�afterall�coatings�have�been�applied.
If�a�vehicle�or�panel�is�to�be�refinished,the�technician�needs�to�identify�the�totalfilm�build�on�the�surface�of�the�part.�OEMpaint�film�thickness�is�generally�about�4�to6�mils.�Some�vehicle�areas�may�have�chip-resistant�coatings�that,�when�measured,will�reveal�a�thicker�film�build.
If�the�film�thickness�is�11�mils�andan�additional�5�mils�are�required�toachieve�proper�refinishing,�the�original
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11�mil�surface�thickness�needs�to�beremoved�down�to�about�5�or�6�mils�beforerefinishing�can�begin.
These�are�examples�of�film�thickness�gauges�thatwork�on�ferrous�metals.
Film�thickness�gauges�are�used�tomeasure�refinish�material�film�thickness.Depending�on�the�type�of�film�thicknessgauge,�it�may�be�able�to�measure�filmthickness�on�a�variety�of�surfaces.�Thisis�because�the�gauge�may�be�designedto�operate�on�any�metal�or�just�steel(ferrous).�Depending�on�the�gauge,�it�maybe�electronic�or�magnetic.
Film�thickness�gauges�measure�filmthicknesses�in�mils�or�microns.�One�milis�0.025�mm�or�1/1000�of�one�inch.�Onemicron�is�1/1000�of�one�millimeter.
It�may�be�necessary�to�remove�refinish�coatings�ifthey�are�too�thick.
When�determining�if�the�finish�is�originalor�not,�identify�how�much�of�the�totalfinish�is�basecoat�/�clearcoat.�This�willhelp�determine�if�there�is�body�fillerused�or�if�the�surface�was�previouslyrefinished.
There�may�be�instances�when�the�vehiclehas�never�been�in�a�collision,�but�the�filmthickness�shows�that�the�panel�has�beenrefinished.�This�happens�due�to�damagethat�occurred�at�the�factory.�Even�thoughthe�vehicle�is�refinished,�it�still�may�beconsidered�an�OEM�finish.
Paint�makers�may�require�stripping�areasthat�have�unidentifiable�refinish�materials.Removing�surfaces�with�unidentifiablematerials�can�aid�in�starting�with�a�goodfoundation�at�which�topcoats�can�beapplied.
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The�poor�color�match�on�this�vehicle�is�an�indicatorthat�it�has�been�refinished.
Signs�that�a�vehicle�has�been�refinishedinclude:
• overspray.• different�colors�on�inner�panel
areas.• a�poor�color�match.• tape�lines.• a�different�surface�texture.
Extreme�film�thickness,�as�shown�here,�is�a�goodindicator�of�filler�material�below�the�finish.
Fillers�are�identified�in�the�refinishing�areausing�a�film�thickness�gauge.�Note�thatwhen�applying�body�filler�over�the�top�ofa�painted�surface,�the�filler�may�expandand�contract.�This�will�cause�contour
mapping�around�the�filler�area.�Contourmapping�is�when�the�filler�area�is�visiblethrough�the�refinished�area.
If�it�is�determined�that�the�refinish�mustbe�removed�over�the�area�of�filler,�specialcare�must�be�taken�to�not�gouge�thesurface�of�the�filler.
KPI�Improvement�Tip
Identifying�the�process�for�fillerapplication�ahead�of�time�will�help�ensurethat�the�filler�does�not�show�through�thefinish�after�the�owner�takes�the�vehiclehome.�This�will�result�in�rework�and�lowerCSI.
This�shows�a�soft�area�of�the�uncured�finish�thateasily�peeled�from�the�pinchweld.
The�need�to�identify�uncured�finishesis�important.�An�uncured�finish�will�beweak�and�will�not�be�resilient�to�abuse.An�uncured�finish:
• may�feel�soft�and�pliable,�almostrubbery.
• will�not�hold�up�to�abuse.�Thefinish�may�chip�or�scratch�easily.
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• featheredge,�if�used, may�havepoor�adhesion�and�may�lift�offduring�sanding.
• may�cause�lifting�to�occur�duringrefinish�applications.
This�shows�a�clearcoat�with�adhesion�problems.
From�the�OEM�or�after�a�complete�refinishprocedure,�there�is�the�possibility�thatthe�coating�materials�will�not�adhereto�the�substrate.�This�may�be�causedby�contaminants�in�the�coatings�or�onthe�surface.�Adhesion�problems�may�beidentified�when:
• the�finish�or�refinish�can�beremoved�easily.
• the�finish�or�refinish�can�beremoved�in�sheets�or�in�wholeintact�sections.
• there�are�areas�of�the�featheredgethat�lift�and�separate�from�eachother.
This�mild�corrosion�issue�must�be�repaired�before�arefinish�is�applied.
Before�any�coatings�can�be�applied,�anysurface�defects�and�/�or�corrosion�must�beidentified�and�corrected.�If�the�defects�arenot�corrected,�a�poor�finish�may�occur.Defects�cannot�be�buried�with�additionalcoatings.�They�must�be�removed�beforemoving�forward.
When�working�over�or�near�corrosion,�theproper�tools,�products,�and�techniquesmust�be�followed�to�obtain�a�qualityrefinish.
Module�Wrap�Up
Topics�discussed�in�this�module�includedtypes�of:
• personal�protection�required�forrefinishing.
• refinish�primers.• OEM�finishes.
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Masking�Or�Removing�Parts
Learning�objectives�for�this�moduleinclude:
• determining�when�to�mask�orremove�a�part.
• identifying�different�types�ofmasking�equipment�and�materials.
• understanding�the�various�types�ofmasking�techniques.
• explaining�how�to�mask�for�primeror�basecoat�/�clearcoat.
• determining�when�finish�coatingsshould�be�removed.
• explaining�the�various�techniquesused�for�coating�removal.
Proper�masking�ensures�overspray�does�not�damagethe�finish�or�parts�away�from�the�repair�area.
Except�for�the�area�to�be�refinished�andany�blending�areas,�the�vehicle�should�becovered�and�protected�from�overspray.
Inadequate�overspray�protection�canextend�the�amount�of�time�needed�by�thedetailer.�When�protecting�adjacent�areasfrom�overspray:
• completely�cover�all�of�the�wheels.• ensure�that�the�trunk�and�engine
compartment�are�coveredcompletely.
• use�aperture�tape�to�preventoverspray�from�entering�panelgaps.
Overspray�that�contacts�adjacent�panels,parts,�or�enters�panel�gaps�needs�to�beremoved�to�provide�a�repair�that�is�asclose to�undetectable�as�possible.
KPI�Improvement�Tip
Making�sure�overspray�is�limited�orprevented�will�reduce�touch�time�andcycle�time.
Door�handle�removal�rather�than�masking�may�berecommended�when�refinishing�a�door�skin.
There�are�no�clear�guidelines�for�when�apart�should�be�masked�or�removed.�Whendeciding�whether�to�mask�or�remove�apart,�consider:
• vehicle�maker�or�paint�makerwarranties.
• part�location.
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Surface�Preparation�and�Masking�(REF02e) 22
• part�access�for�removal�or�formasking.�The�design�of�a�vehicledoor�handle,�molding,�or�emblemmay�determine�what�should�bedone.
• if�the�parts�or�hardware�arereusable.�For�example,�somemoldings,�trim,�and�clips�mayrequire�replacement�if�removed.
• the�ability�to�properly�sand�thesurface�adjacent�to�the�part.Proper�sanding�affects�overallrefinish�material�adhesion,�eitherchemical�or�mechanical.�A�partthat�is�difficult�to�sand�around�mayalso�be�difficult�to�clean�and�mask.
KPI�Improvement�Tip
When�determining�whether�to�mask�orremove�a�part,�it�is�important�to�notecustomer�expectations�with�regard�to�thefinish.�This�can�affect�CSI.
Improper�masking�led�to�improper�refinish�coverage.
Improper�masking�may�require:
• refinishing�or�touching-up�areasthat�were�not�supposed�to�berefinished�but�now�require�it
because�they�were�incorrectlymasked.
• removing�overspray�from�areasthat�were�insufficiently�masked.Overspray�that�contacts�adjacentpanels,�parts,�or�enters�panelgaps�should�be�removed�toprovide�a�repair�that�is�as�closeto�undetectable�as�possible.�Theprocess�of�removing�oversprayextends�the�amount�of�timeneeded�by�the�detailer�and�mayextend�refinishing�time�whensevere.
• replacing�moldings�orweatherstripping�that�werepermanently�damaged�by�theoverspray.
KPI�Improvement�Tip
Performing�rework�and�part�replacementto�compensate�for�overspray�or�bad�tapelines�increases�touch�time�and�decreasescycle�time�as�well�as�create�additionalpart�costs.
Refer�to�the�Video:�Masking�WithPlastic�in�the�presentation.�This�videodemonstrates�how�to�apply�plastic
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Surface�Preparation�and�Masking�(REF02e) 23
sheeting�to�the�vehicle�to�preventoverspray.
Plastic�masking�is�unfolded�over�the�vehicle.
Plastic�masking�materials:
• should�be�resistant�to�thechemicals�and�solvents�containedwithin�refinish�materials.
• is�often�used�to�cover�largerareas, such as�the�body�of�thevehicle�away�from�the�area�beingrefinished.
• range�from�12"�to�16'�in�width.
Paper�masking�is�often�used�in�the�area�adjacent�tothe�panel�being�refinished.
There�are�special�types�of�solvent-resistantpaper�used�to�mask�off�a�vehicle.�Aquality�masking�paper:
• should�hold�up�well�to�waterwhen�wet�sanding.�Traditionalmasking�products�may�not�workwith�waterborne�refinish�materialsbecause�of�high-water�content.
• should�not�have�loose�fibers�thatcan�get�trapped�in�the�refinish.
• should�be�heat�resistant�whenexposed�to�a�spraybooth�bakingcycle.
• may�be�a�special�type�that�issolvent�resistant.
These�papers�can�range�in�sizes�from�3"�to36".
When�masking�a�vehicle�or�part�withmasking�paper�and�tape:
• the�paper�and�tape should�lie�flaton�the�surface�of�the�vehicle.
• hard�paint�lines�may�result�ifthis�is�done�on�the�wrong�areaof�the�vehicle.�Typically,�thistype�of�taping�is�done�away�fromthe�refinish�area�where�refinishmaterials�will�not�be�applied.
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Surface�Preparation�and�Masking�(REF02e) 24
Refer�to�the�Video:�Reverse�Masking�inthe�presentation.�This�video�demonstratesthe�proper�technique�for�applying�reversemasking�to�a�vehicle.
Reverse�masking�requires�folder�the�masking�paperback�against�itself.
Reverse�masking�helps�eliminate�a�hard�tape�line.
Reverse�masking�helps�eliminate�a�hard�tape�line.
Notice�the�curved�edge�of�the�masking.�Thisprovides�the�soft�edge�for�refinishing.
A�technique�called reverse�masking�canbe�used�to�avoid hard�spray�lines.�Reversemasking:
• aids�in�a�soft�transition�to�themasking�paper.
• is�done�by�taping�the�maskingpaper�over�the�repair�area�andfolding�the�masking�paperbackwards.�This�creates�an�arch�inthe�paper,�allowing�a�soft,�invisibletape�line.
• is�used�when�masking�alongbodylines�or�other�natural�breakswhen�only�part�of�a�panel�is�to�berefinished�or�blended.�It�can�alsobe�used�when�masking�jambs.
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Surface�Preparation�and�Masking�(REF02e) 25
A�variety�of�masking�tape�thicknesses�are�used�forthe�masking�process.
Automotive�grade�masking�tape:
• differs�from�household�tape.• is�available�in�a�variety�of�widths
and�colors.• often�has�a�special�treatment�to
allow�for�solvent�and�moistureresistance�that�minimizes�bleedthrough.
Width�sizes�for�automotive�maskinginclude:
• 1/4�-�1/2".• 3/4�-�1-1/2".• 2�-�3".
There�are�specialty�tapes�used�for�coveringtrim,�outlining�door�handles,�coveringdoor�locks,�and�around�light�assemblies.These�tapes�come�in�widths�of:
• 1/16�-�3/32".• 1/8�-�3/16".• 1/4�-�3/8".
• 1/2�-�3/4".
Different�types�and�brands�of�maskingtape�may�be�listed�in�productbooks�as�both�metric�and�standardmeasurements.
Refer�to�the�Video:�Back�Masking�in�thepresentation.�This�video�demonstratesthe�proper�technique�for�applying�backmasking�to�a�vehicle.
Back�masking�is�often�used�on�the�fuel�filler�area.
Back�masking:
• prevents�overspray�from�gettingbehind�panels.
• is�used�for�holes�in�panels,openings,�and�around�edgesof�panels.�For�example,�back
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Surface�Preparation�and�Masking�(REF02e) 26
masking�is�used�around�a�wheelopening,�fuel�filler�cap�opening,door�opening,�trunk�opening,window�openings�where�the�glasshas�been�removed,�and�doorhandle�and�lock�cylinder�holes.
• is�applying�masking�tape�to�theunderside�edge�of�the�opening�sothat�half�of�the�tape�hangs�over�theedge.�The�masking�tape�should�bevisible�along�the�entire�edge�of�theopening.
• is�applying�masking�paper�to�theadhesive�side�of�the�masking�tapethat�is�exposed�in�the�opening.If�the�opening�is�small�enough,masking�tape�may�be�used�to�fillthe�opening�and�masking�papermay�not�be�required.
These�are�examples�of�tape�types�used�for�fine�linemasking.
Fine�line�masking�is�used�when�maskinga�flush-mounted�part.�For�example,�a�partthat�is�tight�to�a�panel�and�has�a�smallrubber�grommet�around�it�may�requirefine�line�masking.�When�fine�line�or�flush-mounted�masking:
• mask�up�to�3�mm�of�the�edge�ofthe�part.
• use�6�mm�fine�line�tape�and�maskup�to�the�edge�of�the�part.
• leave�a�“tail”�or�tab�on�the�end�ofthe�masking�tape�to�make�removaleasier.
• remove�the�fine�line�tape�while�theclearcoat�is�still�wet.
Fine�line�masking�tape�may�also�be�usedwhen�two-tone�painting�and�custompainting.
Refer�to�the�Video:�Foam�Tape�Masking�inthe�presentation.�This�video�demonstrateshow�to�apply�foam�tape�in�body�aperturesto�prevent�overspray.
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Surface�Preparation�and�Masking�(REF02e) 27
These�are�examples�of�different�types�of�aperturetape�that�are�available,�with�different�widths�andthicknesses.
Aperture�tape�is�being�applied�to�the�door�opening.
Aperture�tape�is�applied�around�the�entire�dooropening,�along�the�dog�leg�area�and�outer�rockerpanel.
Aperture�tape,�or�jamb�masking, is�asoft,�foam-type�material�used�to�preventunwanted�overspray.�It�also�provides�asoft edge�to prevent�tape�lines�in�the�jamb
areas. Aperture�tape�is�frequently�appliedin�between:
• door�gaps.• deck�lid�to�quarter�panel�gaps.• the�hood�to�fender�gaps.• fuel�door�gaps.
Refer�to�the�Video:�Lift�Tape�Masking�inthe�presentation.�This�video�demonstrateshow�to�use�lift�tape�to�hold�the�trim�awayfrom�the�vehicle�surface�for�refinishing.
This�shows�the�various�thicknesses�and�types�oflifting�tape�that�are�available.
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Surface�Preparation�and�Masking�(REF02e) 28
Lifting�tape�is�being�applied�to�quarter�glass�molding.
Relief�cuts�in�the�lifting�tape�are�used�to�help�maskthe�corner�of�the�quarter�glass.
Lifting�tape�is�applied�around�the�entire�quarter�glassto�pull�the�molding�away�from�the�refinish�area.
Lifting�tape,�or�trim�masking�tape:
• is�used�around�trim�and�moldings,including�flush-mounted
windshields,�side�glass,�andbackglass�moldings.
• holds�the�trim�or�molding�up�andaway�from�the�surface�so�thatrefinish�materials�can�be�appliedto�the�surface�beneath�the�trim�ormolding.
• may�have�a�plastic�edge,�adhesive,or�be�a�plastic�rope-like�materialthat�is�inserted�under�the�trim�ormolding�to�lift�the�trim�or�moldingoff�of�the�surface.
Refer�to�the�Video:�Masking�For�Primer�inthe�presentation.�This�video�demonstrateshow�to�mask�for�primer�application.
This�area�is�being�masked�for�primer�application.
When�masking�before�applying�primers:
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Surface�Preparation�and�Masking�(REF02e) 29
• spray�lines�should�be�soft.�Do�notmake�a�hard�spray�line.
• mask�off�the�jambs�from�overspray.• keep�the�area�as�small�as�possible.
The�entire�panel�may�not�need�tobe�primed.
When�masking�for�a�blend�area,�usemasking�techniques�designed�for�blendareas�such�as�reverse�masking.
This�masking�machine�is�designed�to�hold�multiplesizes�and�various�types�of�masking�materials.
Masking�machines:
• are�used�to�hold�paper,�plastic,and�tape�rolls.
• are�mobile�carts.�A�technician�canuse�a�masking�machine�to�takea�variety�of�masking�materials�tothe�area�where�masking�is�to�beperformed.
• apply�the�tape�to�the�paper�whendispensed.
The�masking�tape�is�pulled�back�against�itself�duringremoval.
When�removing�masking�materials:
• the�tape�should�be�pulled�off�sothat�it�is�flat�against�itself.
• the�tape�should�be�removed�whenthe�vehicle�temperature�is above60°F.�At�lower�temperatures,�theadhesive�may�separate�from�thetape.
• the�tape�should�not�be�left�on�thevehicle�any�longer�than�necessary.Water�and�sunlight�can�deterioratethe�materials�if�they�are�exposedfor�an�extended�period�of�time.
• consider�leaving�the�maskingmaterials�on�until�after�the�vehiclehas�been�detailed.�Masking�keepsbuffing�compound�out�of�hard-to-reach�areas.�Masking�canhelp�reduce�the�amount�of�timerequired�to�clean�the�vehicle�afterrefinishing�and�buffing.
• dispose�of�it,�do�not�throw�it�onthe�floor.�Masking�materials�on�thefloor�results�in�clutter�and�createspersonal�safety�concerns.
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Surface�Preparation�and�Masking�(REF02e) 30
Liquid�masking�is�available�in�one�gallon�jugs,�as�wellas�larger�sizes.
Spray�Masking�is�sprayed�away�from�the�area�beingrefinished,�such�as�the�windshield�on�this�vehicle.
Spray�masking�can�also�be�applied�to�tires.
Spray�masking�is�used�to�help�protectsurfaces�from�overspray.�This�water-basedproduct�is�applied�using�a�spray�gun�andallowed�to�dry.
When�applying�the�spray�masking,�be�sureto�cover�the�repair�area.�This�prevents�thespray�masking�from�contaminating�thearea�to�be�refinished.�After�the�maskingmaterial�has�been�applied:
• remove�the�overspray�with�adamp�sponge�if�any�oversprayhas�contacted�the�area�to�berefinished.
• do�not�expose�spray-masked�areasto�direct�sunlight.
Some�materials�may�“cobweb”�whensprayed.�This�may�occur�from�materialthat�is�too�thick�or�from�ambienttemperatures�being�too�high.
To�remove�spray�masking:
• rinse�off�the�vehicle�with�waterand�allow�the�material�to�dissolve.
• wash�the�vehicle�using�soap�andwater.
Finish�Removal
A�thickness�of�14.5�mils�means�that�some�of�thefinish�must�be�removed�before�refinishing.
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Surface�Preparation�and�Masking�(REF02e) 31
Paint�film�thickness�must�be�measuredbefore�application�of a�refinish.�Asdiscussed�earlier,�if�the�coating�thicknesswill�be�over�11�mils,�some�finish�removalis�required.�This�can�be�accomplishedby:
• sanding�the�finish�down�to�alevel�that�is�acceptable�to�beginrefinishing�again.
• completely�removing�the�coatings.When�a�finish�is�completelyremoved,�all�coatings�are�removeddown�to�the�bare�substrate.
Hand�sanding�can�be�used�to�reduce�the�thicknessof�a�finish.
When�removing�or�altering�the�filmthickness,�sanding:
• effectively�removes�texture.• levels�the�surface�of�minor
imperfections.• will�remove�more�material�than
scuffing.
Performing�the�sanding�process�can�bedone�by�hand�using�various�types�of
sanding�blocks,�or�done�using�a�machine.There�are�many�types�of�sanding�gritsavailable,�ranging�from�P36�to�P1200,depending�on�the�system�used.
A�variety�of�grits�are�used�to�reduce�the�thickness�ofa�finish.
Reducing�the�finish�to�a�proper�thicknessor�removing�the�finish�altogether�allowsfor�a�solid�foundation�to�apply�refinishmaterials.�Methods�used�to�partiallyremove�a�finish�include:
• sanding�as�necessary�using�therecommended�grit.
• using�coarse�grit�materials�andworking�to�finer�grit.�A�generalrule�is�to�not�step�more�than100�grit�when�using�sandpaperbetween�36�and�500�grit.�A�200-grit�step�can�be�made�when�usingsandpaper�between�600�and�1000grit.
The�paint�makers�may�providerecommendations�for�grit�type.
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Surface�Preparation�and�Masking�(REF02e) 32
(Left�to�right)�Sand,�corn,�or�walnut�media�can�beused�for�media�blasting�a�finish.
Plastic,�such�as�this,�can�also�be�used�for�mediablasting.
Media�blasting�is�the�process�of�throwinghigh-velocity�particles�at�a�substrate�tostrip�away�finish�coatings.�This�type�ofcoating�removal�process�is�generallyreserved�for�restoration�jobs,�but�can�beused�for�collision�repair.
There�are�many�different�types�of�materialsthat�may�be�used�for�media�blastingfinishes�and�corrosion.�These�materialsinclude:
• plastic.• aluminum�oxide.• glass.• walnut�shells.
• peach�pits.• corn�cob�material.• wheat�hulls.• sand.
Personal�Safety
Media�blasting�with�silica�sand�maycause�lung�infections�and�disease,�suchas�silicosis,�tuberculosis,�and�pneumonia.Silicosis�is�an�irreversible�scarring�of�theinner�lung�tissue.�This�happens�when�thesilica�dust�is�inhaled�and�the�lung�tissuecreates�scars�from�attempting�to�repair�thedamage�caused�by�the�sand�irritation.�Forthis�reason,�sand�is�rarely�used�as�thereare�a�variety�of�safer�alternatives�for�mediablasting.
The�use�of�other�media�may�not�posethe�same�health�threat,�although�the�by-product�of�the�surface�being�blasted�maybe�just�as�harmful.�Harmful�irritants�maybe�found�in�the�stripped�material.
Portable�media�blasters�can�be�used�to�remove�afinish.
Some�concerns�and�problems�that�maybe�encountered�with�media�blasting�mayinclude:
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Surface�Preparation�and�Masking�(REF02e) 33
• excessive�heat�that�may�warpparts.�Some�media�generates�lessheat�than�others.�For�example,aluminum�oxide�creates�more�heatthan�walnut�shells.
• excessive�abrasion�and�aggressionwith�finish�removal.�This�canbe�addressed�with�differentmedia�types.�Soda�blasting�ismuch�less�aggressive�and�isgood�for�removing�finishes�onsofter�substrates�such�as�plastic.However,�it�is�not�a�good�optionfor�removing�heavy�rust�or�bodyfiller.
• difficulty�cleaning�media�out�oftight�areas�and�pivot�points.
• conflicts�with�the�weather,�whichmay�restrict�outdoor�use.
Heavyweight�tape�can�protect�glass�and�trim�fromdamage.
When�using�blasting�media�to�removea�finish�from�a�vehicle,�the�appropriateheavyweight�protective�masking�and�tapeneeds�to�be�applied�to�protect:
• glass.• bright�metal.
• plastic�trim.• adjacent�panels.
There�are�a�number�of�masking�vendorsthat�offer�thicker�material�that�canwithstand�media�blasting.
Module�Wrap�Up
Topics�discussed�in�this�moduleincluded:
• when�to�mask�or�remove�a�part.• different�types�of�masking
equipment�and�materials.• the�various�types�of�masking
techniques.• how�to�mask�for�primer�or
basecoat�/�clearcoat.• when�finish�coatings�should�be
removed.• the�various�techniques�used�for
coating�removal.
Module�3�-�Spray�Gun�TechniqueTextbook
Surface�Preparation�and�Masking�(REF02e) 37
Spray�Gun�Setup
Learning�objectives�for�this�moduleinclude:
• listing�steps�for�setting�up�the�spraygun.
• identifying�causes�and�listingcorrective�action�for�incorrectspray�patterns.
• determining�proper�travel�speedand�overlap�for�best�finishapplication.
• determining�proper�distance�tothe�panel�and�proper�triggeringtechnique.
• identifying�steps�for�sprayingdifficult�areas.
This�is�an�example�of�an�air�pressure�gauge�on�aspray�gun.
When�setting�up�a�high-volume,�low-pressure�(HVLP)�spray�gun:
• adjust�the�inlet�pressure.�The�spraygun�maker�will�recommend�aspecific�inlet�pressure�at�the�baseof�the�spray�gun.
• measure�the�air�cap�pressure�andadjust�as�necessary�for�proper
airflow.�Too�much�or�too�littleairflow�can�cause�problems�whenapplying�material.
• a�special�gauge�/�cap�can�be�usedfor�monitoring�air�pressure�at�theair�cap.�There�are�two�gauges�onsome�air�pressure�caps.�Thesegauges�measure�air�pressure�at�theair�cap�horn�and�near�the�fluidnozzle.
KPI�Improvement�Tip
Proper�settings�on�the�paint�gun�willensure�that�there�are�fewer�defects�in�thefinish�while�controlling�the�amount�ofmaterial�deposited�on�the�panel.
Setting�the�proper�air�pressure�ensures�the�refinishmaterial�is�applied�most�efficiently.
When�adjusting�air�pressure�at�the�inlet�ofthe�spray�gun,�keep�in�mind�that:
• spray�gun�makers�will�state�aspecific�inlet�pressure.
• the�proper�inlet�air�pressure�willgive�10�psi�at�the�air�cap�with�thefan�control�wide�open.
• as�the�fan�control�is�closed,�the�aircap�pressure�increases.
Module�3�-�Spray�Gun�TechniqueTextbook
Surface�Preparation�and�Masking�(REF02e) 38
• air�regulators�adjust�the�air�supplyto�pressures�required�by�the�spraygun�maker�and�for�other�powertools.�Begin�adjusting�the�airpressure�at�the�regulator�andallow�for�pressure�drops�if�long�airhoses�are�being�used.�Ultimately,the�pressure�valve�at�the�spraygun�should�be�used�to�measureinlet�pressure.�An�air�regulatormaintains�a�constant�air�pressureand�air�volume.�A�cheater�valverestricts�airflow�and�creates�anunstable�air�pressure�and�airvolume.�Cheater�valves�should�notbe�used�with�spray�equipment.
These�spray�test�patterns�illustrate�problems�with�thespray�gun.
A�test�spray�pattern�is�used�to�ensure�thegun�is�applying�an�even�coat�to�the�panel.A�test spray�pattern�should�be�sprayed:
• before�applying�any�refinishmaterial�to�the�vehicle.�That�wayany�problems�can�be�corrected.
• on�masking�paper,�not�on�thespraybooth�walls.
• by�holding�the�spray�gun�about�8�-10"�from�the�surface.
• by�pulling�the�trigger�and�releasingit�quickly.
The�spray�pattern�should�be�a�slender,vertical�oval,�with�even�coverage.�Animproper�spray�pattern�may�appearfluttery,�like�a�crescent�moon,�or�have anirregular�pattern,�wide�center�pattern,�or�aconstricted�center�pattern.
Clogs�in�any�of�these�orifices�can�cause�applicationissues.
To�perform�a�quality�refinish,�the�spraypattern�needs�to�be�uniform�and�equal.�Ifthe�pattern�is�not�uniform�with�the�amountof�material�that�is�deposited,�the�finishwill�have�a�poor�appearance.�A�balancedspray�pattern�has�an�equal�amount�ofmaterial�deposited�in�the�spray�pattern.
Improper�patterns�will�show�heavy�orlight�spots�in�the�pattern.�A�pattern�that�isdepositing�heavy�on�the�top�or�the�bottomindicates�that�material�has�dried�aroundthe�outside�of�the�air�cap.�The�air�cap�willneed�to�be�removed,�cleaned,�and�a�newtest�pattern�sprayed.�Two�other�types�ofspray�pattern�problems�are:
Module�3�-�Spray�Gun�TechniqueTextbook
Surface�Preparation�and�Masking�(REF02e) 39
• crescent-shaped�patterns,�causedby�restrictions�in�the air�passage�atthe�air�cap�horn.
• figure�8�patterns,�caused�byatomizing�air�pressure�that�istoo�high�for�the�viscosity�of�thematerial�being�sprayed.
Proper�distribution�is�shown�by�an�even�drip�acrossthe�spray�pattern.
When�testing�for�proper�distribution:
• rotate�the�air�cap�so�that�theears,�or�air�horns,�are�straight�upand�down.�This�will�produce�ahorizontal�spray�pattern.
• hold�the�spray�gun�8�-�10"�fromthe surface.
• pull�the�trigger�until�the�refinishmaterial�begins�to�run.
• the�runs�will�be�about�the�samelength�if�all�adjustments�arecorrect.�If�the�center�sags�more,there�is�not�enough�pattern�air.Either�turn�out�the�pattern�controlknob,�turn�in�the�fluid�controlknob,�or�increase�the�air�pressure.If�the�sides�sag�more,�the�airpressure�is�too�high�or�the�patterncontrol�knob�is�set�too�wide.
Checking�a�spray�gun�setup�chart�helps�ensureproper�coverage.
Both�spray�gun�and�paint�makers�compilea�list�of�information�for�the�refinishtechnician.�This�information�helpseliminate�the�guesswork�for�what�fluidneedle,�fluid�nozzle,�and�air�cap�shouldbe�used�for�specific�materials�beingsprayed.
This�chart�offers�a�starting�point�for�thetechnician�when�setting�up�a�spray�gun.Paint�makers�post�the�required�fluidneedle�and�nozzle�size�for�optimumspray�results.�Refer�to�their�spray�gunspecifications�for�which�fluid�needle�andnozzle�will�work�the�best.
Spray�Gun�Application�Techniques
Proper�spray�gun�use�ensures�a�smooth,�even�finish.
Module�3�-�Spray�Gun�TechniqueTextbook
Surface�Preparation�and�Masking�(REF02e) 40
To�properly�use�a�spray�gun:
• hold�the�spray�gun�the�properdistance�from�the�panel.
• hold�the�spray�gun�level�andperpendicular�to�the�panel.�Keepthe�spray�gun�perpendicular�to�thesurface�at�all�times,�following�theangles�and�curves�of�the�vehiclewith�a�wrist�motion.
• begin�moving�before�pulling�thetrigger.�This�should�occur�beforenearing�a�refinish�panel.�Refinishmaterial�application�should�startjust�before�reaching�the�edge�ofthe�panel.
• move�the�spray�gun�in�a�steady,even�motion.
• release�the�trigger�before�stoppingmovement�of�the�spray�gun.
• do�not�fan�the�spray�gun.�Fanningis�permitted�only�when�spraying�asmall�spot�repair�area.
This�shows�the�adjustment�for�spray�gun�air�pressure.
This�shows�the�location�for�the�spray�gun�fanadjustment.
This�shows�the�adjustment�location�for�the�fluidneedle.
When�adjusting�a�spray�gun,�therefinish�technician�needs�to�be�awareof�what�adjustments�are�needed.Adjustments options�on�the�spray�guninclude:
• fan�width,�which�can�be�adjustedfrom�a�small�diameter�circleto�a�large�oblong�pattern.�Thefan�width�adjustment�knobis�generally�on�the�top�of�thespray�gun�body.�Turn�the�controlknob�all�the�way�in�to�create�asmall,�round�pattern�with�densecoverage.�Turn�the�control�knobgradually�out�to�form�a�vertical,elongated�pattern�with�lighter
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Surface�Preparation�and�Masking�(REF02e) 41
coverage.�If�turned�too�far,�thepattern�will�be�too�heavy�on�theends�and�too�light�in�the�middle.
• the�amount�of�paint�deposited,or�fluid�adjustment. It�can�beadjusted�to�a�lighter�deposition�byturning�the�adjustment�in,�and�aheavier�deposition�by�backing�theadjustment�out.�The�fluid�controladjustment�knob�is�generallylocated�below�the�fan�widthadjustment�knob�on�the�spray�gunbody.
• air�pressure.�Air�pressure�at�thegun�inlet�is�often�provided�by�thespray�gun�maker.�The�proper�inletair�pressure�will�give�a�reducedpressure�at�the�air�cap�with�thefan�control�wide�open.�The�airpressure�at�the�cap�for�an�HVLPspray�gun�is�10�psi.
Improper�travel�speed�can�cause�drips�or�poorcoverage.
The�travel�speed�is�the�rate�that�the�spraygun�is�moved�along�the�panel�surface.The�travel�speed�of�a�spray�gun�can�affectfinish�appearance.�It�should�be�steady�andeven. If�the�travel�speed�is�too:
• slow,�the�material�may�sagand�run.�This�type�of�finish�isunacceptable,�and�will�need�tobe�sanded�down�and�possiblyreapplied.
• fast,�the�material�lays�down�drywith�a�rough�texture.�This�finishwill�not�present�an�acceptableappearance.
A�75%�overlap�helps�ensure�adequate�coverage.
When�spraying�refinish�materials,�anadequate�and�sufficient�overlapping�of�thematerial�is�required.�Most�paint�makersand�spray�gun�makers�are�recommendingan�overlap�of�75%�to�get�completecoverage�and�hiding�of�the�materialbeing�sprayed.�If�proper�overlap�is�notachieved,�extra�material�and�steps�may�berequired�to�obtain�the�desired�results.�Toobtain�proper�overlap�when�completelyrefinishing�a�panel:
• start�with�the�first�pass�on�the�topof�the�panel�or�on�the�bottomdepending�on�personal�preference.
• spray�each�alternate�pass�in�theopposite�direction.�For�example,the�first�pass�is�made�from�left�to
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Surface�Preparation�and�Masking�(REF02e) 42
right,�and�the�second�pass�is�madefrom�right�to�left.
• always�blend�the�next�pass�into�thewet�edge�of�a�previously�sprayedpanel.�Improper�overlap�canresult�in�uneven�film�thickness,contrasting�color�hues,�and�sags�orruns.�Careful�triggering�and�spraygun�control�will�help�reduce�thesags�and�runs�in�overlapped�areas.
When�spraying�metallics�or�pearls,�acontrol�coat�is�often�recommended�toensure�proper�flake�orientation.�A�controlcoat�has�an�overlap�of�85�-�90%.�Butthis�is�done�with�air�pressure�reduced�by40%.
Reverse�priming�is�done�by�laying�down�smallerconsecutive�coats.
Reverse�priming�is�the�process�of�applyinga�larger�of�coating�of primer first,�followedby�progressively�smaller�applications.
Reverse�priming�is�used�to:
• ensure�a�smoother�surface.• allow�for�easier�sanding.• reduce�the�amount�of�overspray
edges�when�spot�priming.
Advantages�of�reverse�priming�include:
• less�overspray�on�the�edges�ofeach�coat�(less�texture�and�betteradhesion).
• less�potential�for�trapped�solventto�cause�die�back�or�solventpopping.
• edges�being left�open,�allowingsolvent�to�escape,�which�decreasesthe�dry�time.
• an�edge�that�is�easier�to�featherinto�the�surrounding�existingfinish.
Proper�distance�to�the�panel�ensure�adequatecoverage�while�minimizing�the�potential�for�sags�orruns.
The�distance�that�a�spray�gun�is�heldrelative�to�the�panel�surface�(also�calledsetback)�can�have�effects�similar�to�that�oftravel�speed.
A�spray�gun�that�is�too:
• close�will�deposit�too�muchrefinish�material�on�the�panel,potentially�causing�runs�and�sags.
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Surface�Preparation�and�Masking�(REF02e) 43
These�defects�will�need�to�beremoved.
• far�back�can�have�a�dry,�rough,or�poor�coverage�effect.�This�canalso�lead�to�excessive�overspray,causing�wasted�material�and�time.
Proper�trigger�technique�can�help�create�bettertransfer�efficiency.
Triggering�the�spray�gun on�at�thebeginning�of�a�spray�stroke�and�off�at�theend�of�a�spray�stroke:
• allows�for�less�use�of�paint�andmaterials.
• reduces�the�amount�of�materialdeposited�at�the�edge�of�thepanels.�Failure�to�trigger�exactlyover�the�edge�of�the�panel�canresult�in�excessive�film�build.
Arching�and�heeling�techniques�can�help�create�asolid�finish�with�good�transfer�efficiency.
Heeling�is�allowing�the�spray�gun�to�tilt.Arching�or�fanning�is�failure�to�keep�thespray�gun�parallel�to�the�surface.�Bothheeling�and�arching�can�result�in�unevenfilm�thickness,�orange�peel,�dry�spray,�andexcessive�overspray.
Spraying�the�wheelhouse�requires�good�technique�toavoid�paint�defects.
Difficult�areas�to�spray�may�includecorners�and�edges�of�panels.�Whenspraying�difficult�areas:
• it�may�be�best to�spray�these�areasfirst.
• the�pattern�size�and�air�pressuremay�need�to�be�reduced.
• it�may�be�best�to�hold�the�spraygun�closer�than�normal,�for
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Surface�Preparation�and�Masking�(REF02e) 44
example,�1�-�2"�away�from�thepanel.
• it�may�help�to�aim�directly�at�thecenter�of�the�problem�area.
Refer�to�the�Video:�Proper�SprayTechnique�in�the�presentation.�Thisvideo�discusses�concepts�of�proper�spraytechnique�and�how�it�ensures�a�qualityfinish.
Module�Wrap�Up
Topics�discussed�in�this�moduleincluded:
• steps�for�setting�up�the�spray�gun.• causes�and�listing�corrective
action�for�incorrect�spray�patterns.• proper�travel�speed�and�overlap
for�best�finish�application.• proper�distance�to�the�panel�and
proper�triggering�technique.• steps�for�spraying�difficult�areas.
Module�4�-�Substrate�PreparationTextbook
Surface�Preparation�and�Masking�(REF02e) 47
Preparing�Substrates
Learning�objectives�for�this�moduleinclude:
• describing�how�to�prepare�anOEM�finish�for�topcoats.
• describing�what�steps�should�beperformed�to�prepare�E-coatedparts�for�refinishing.
• identifying�refinish�considerationsfor�plastic,�steel,�and�aluminum.
• listing�the�importance�of�sprayoutpanels.
• identifying�specialty�spray�areasand�refinish�considerations.
Featheredging�out�the�OEM�finish�helps�eliminate�anoticeable�repair�area.
Before�refinishing,�an�OEM�finish:
• may�only�need�to�be�cleaned�andscuffed�or�sanded.
• often�provides�a�sound�substratefoundation.
• generally�does�not�need�to�bepartially�or�completely�removed�inpreparation�of�a�refinish.
Sometimes�minor�defects,�such�as�this�hair,�cancome�from�the�factory�and�may�require�repair.
Before�refinishing�an�OEM�finish,�thefinish�should�be�checked�and�inspectedfor�soundness.�Some�OEM�finishes�mighthave:
• problems�originating�from�thefactory.
• excessive�or�inadequate�film�buildareas.
• lack�of�adhesion.
When�working�on�an�OEM�finish,�propersteps�need�to�be�followed�to�create�aproper�repair.
Scuffing�the�surface�of�a�finish�adjacent�to�the�repairarea�will�allow�good�topcoat�adhesion.
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Surface�Preparation�and�Masking�(REF02e) 48
Scuffing�is�a�form�of�surface�preparationthat:
• is�the�least�aggressive.• is�used�to�degloss�the�clearcoat.
Scuffing�is�not�aggressive�enoughto�remove�orange�peel�or�reducefilm�thickness.
• aids�in�adhesion�for�new�parts�thatrequire�light�abrasion.
• may�be�done�using�a�scuff�pad,wet�or�dry�sanding�with�fine�gritsandpaper,�or�a�paste-type�sandingmaterial.
• should�be�done�without�creatingscratches�or�breaking�into�theundercoat.
• is�done�using�moderate�pressure.• may�be�done�after�surface
reconditioning�to�remove�nibsand�dust�specks�on�primers�andsealers.
Like�sandpaper,�scuff�pads�come�in�a�variety�of�grits.
Scuffing�pads:
• are�made�of�a�nylon-type�materialor�a�woven�plastic�abrasive.
• typically�do�not�have�a�gritnumber�listed,�but�will�be�color-coded,�or�labeled�as,�coarse�toultra-fine.
• may�be�used�with�sanding�paste�todegloss�an�area�for�refinishing.
• may�be�used�to�prepare�areas�forblending.
• are�used�in�areas�where�a�DAsander�cannot�adequately�access.
• may�be�used�as�a�final�sandto�ensure�that�areas�that�weremissed�in�the�earlier�preparationstages�are�properly�prepared�forrefinishing.
This�previously�refinished�area�has�adhesionproblems.
Some�surfaces�requiring�refinishing�mayhave�been�previously�refinished�at�anearlier�time.�Previously�refinished�areasmay:
• have�multiple�layers�of�materialbuilt�up.
• be�dry,�but�not�completely�cured.• have�poor�adhesion�qualities.• require�partial�finish�removal
because�of�excessive�film
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Surface�Preparation�and�Masking�(REF02e) 49
thickness�or�improper�materialapplication.
• have�an�acceptable�filmthickness�that�will�allow�topcoatapplication.
When�refinishing�a�panel�that�waspreviously�refinished,�it�may�be�helpfulto�know�what�paint�system�was�used,�ifpossible.
Inspecting�the�E-coated�part�upon�delivery�can�helpidentify�potential�refinish�problems.
Some�parts�come�shipped�with�E-coatalready�applied.�When�working�withparts�that�shipped�with�E-coat,�perform�asolvent�test,�if�needed.�This�verifies�thatE-coat�is�sound�and�is not�just�a�shippingcoating.�Solvent�testing�is�performed�toidentify�if�a�substrate�will�hold�up�to�thereducing�agents�that�will�be�applied�to�therefinish�area.
No�coating�transfer�to�the�cloth�generally�means�thepart�has�E-coat�applied.
A�solvent�test�is�easy�to�perform,�andshould�always�be�performed�if�there�is�anyquestion�as�to�the�quality�of�the�E-coat.�Toperform�a�solvent�test:
• dampen�a�cloth�with�reducer�orthinner.
• rub�the�dampened�cloth�on�thepanel�surface.
If�the�material�transfers�to�the�cloth,�it�isunstable�and�needs�to�be�removed.
KPI�Imrovement�Tip
A�solid�foundation�is�key�for�ensuringa�quality�finish�that�is�appealing�to�thecustomer.�This�ensures�no�chipping�ordelamination�after�the�vehicle�leaves�therepair�facility.
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Surface�Preparation�and�Masking�(REF02e) 50
Wiping�an�E-coated�panel�with�solvent�helps�prepareit�for�basecoats.
If�the�E-coat�is�sound,�the�E-coated�surfacemust�be�prepared�for�topcoat�applicationby:
• cleaning�using�soap�and�water.• cleaning�using�a�wax�and�grease
remover.• scuffing�the�surface�of�the�E-coat
to�help�aid�in�adhesion�of�thetopcoats.
• blowing�and�tacking�off�thesurface�with�clean�compressed�airand�a�tack�cloth.
• applying�sealer.�Some�refinishsystems�allow�a�sealer�to�beapplied�directly�to�the�E-coatwithout�scuffing�or�sanding.�Thisallows�the�scuffing�and�primingstep�to�be�bypassed.
Featheredging�is�a�standard�repair�technique�used�tosmooth�out�the�repair�area.
Featheredging�is�used�to�gradually taperout�the�repair�area so�there�is�a�smootharea�with�no�lines�that�can�showthrough�a�finish.�This�ensures�there�isno�disruption�to�the�appearance�of�therefinish�coatings.�If�body�filler�is�used�ina�featheredged�area,�the�filler�should�notcontact�the�finish�area.
When�creating�a�featheredge,�thesurface:
• should�be�sanded�with�P180�gritas�a�start.�As�a�featheredge�isworked�out�into�the�blend�area,sanding�media�can�be�increasedin�steps�of�up�to�100�grit�at�a�time,up�to�500�grit.�This�allows�for�theprevious�grit�sandscratches�to�beremoved�quickly�and�effectively.When�using�sanding�materialabove�500�grit,�there�can�be�ajump�of�up�to�200�grit�at�a�time,up�to�1,000�grit.�A�500�grit�jumpbetween�materials�can�be�usedwith�1,000�grit�and�above.
• needs�to�be�leveled�with�a�primer-surfacer�and�then�block-sandedsmooth.�Areas�that�will�not�be
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Surface�Preparation�and�Masking�(REF02e) 51
covered�with�primer-surfacershould�only�be�scuffed�or�sandedusing�P500�grit�sanding�material.
Refer�to�the�Video:�Preparing�A�PartFor�Primer�in�the�presentation.�Thisvideo�demonstrates�sanding�techniquescommonly�used�to�prepare�a�part�forprimer�application.
Plastics
The�plastic�bumper�cover�is�being�checked�for�anysurface�defects.
When�refinishing�plastic�parts,considerations�include:
• identifying�the�type�of�plasticmaterial�used.�Categories�includerigid�vs.�flexible.
• paint�maker�recommendationsfor�plastic�cleaners�or�otherpreparation�steps.
• determining�if�an�adhesionpromoter�must�be�applied�to�thesurface�before�coating�application.Adhesion�promoters�are�typicallyrequired�on�polyolefin�plastics.
Rigid�plastics�are�difficult�to�bend.
Rigid�plastic�parts�may�include:
• sheet-molded�compounds�(SMC).• fiberglass.• polycarbonate.
Before�refinishing�plastic,�the�refinishtechnician�should:
• determine�if�the�refinish�materialwill�require�the�use�of�a�flexadditive.
• understand�that�the�part�maycontain�fibers�that�can�wickcleaners�and�solvent�into�thesurface�and�not�be�released.
Module�4�-�Substrate�PreparationTextbook
Surface�Preparation�and�Masking�(REF02e) 52
Flexible�plastics,�commonly�found�in�bumper�covers,are�easy�to�bend.
Flexible�plastic�parts�may�include:
• polyamide.• polyurethane.• thermo-polyurethane.
Some�common�parts�include�bumpercovers�and�body�trim.
Before�any�work�or�refinishing�of�theseproducts�can�begin,�determine:
• if�the�refinish�material�will�requireflex�additive.
• the�preparation�steps.�Aninterior�part�may�get�prepareddifferently from�an�exterior�part.
Refer�to�the�Video:�Preparing�Bare�PlasticParts�in�the�presentation.�This�videodiscusses�concepts�on�preparing�plasticparts�for�refinishing.
Bare�And�Repaired�Steel
The�bare�steel�will�need�a�specific�primer,�suchas�self-etching�primer,�before�a�primer-surfacer�isapplied.
When�working�with�bare�steel�parts,�therefinish�technician�must�determine�if�thepart:
• is�galvanized.• requires�a�metal�cleaner�and
conversion�coating.• requires�a�self-etching�primer.• requires�sanding�or�scuffing.
Module�4�-�Substrate�PreparationTextbook
Surface�Preparation�and�Masking�(REF02e) 53
Epoxy�primer�may�be�used�over�bare�steel.
Refinishing�products�that�can�be�appliedto�bare�metal�substrates�include:
• metal�preparation�/�conversioncoatings.�These�coatings�may�beused�before�epoxy�primer,�butare�generally�not�used�with�self-etching�primer�or�over�body�filler.
• zinc�chromate�/�phosphateprimers,�which�cover�the�substratebut�do�not�etch�into�the�surface.
• direct-to-metal�or�etching�primers.• epoxy�primers.• urethane�and�2K�primers�that�are
easy�to�sand,�provide�high�build,and�have�minimal�shrinkage.�Asealer�may�not�be�required.
Refer�to�the�Video:�Preparing�Bare�AndRepaired�Steel�in�the�presentation.�Thisvideo�discusses�concepts�on�preparingbare�metal�and�repaired�steel�parts.
Bare�And�Repaired�Aluminum�Parts
Scuffing�the�surface�of�an�aluminum�hood�isrecommended�before�applying�the�recommendedprimer.
When�working�with�aluminum:
• do�not�use�grits�coarser�than�P80.Aluminum�scratches�very�easilyand�can�be�difficult�to�mask�due�tothe�softness�of�aluminum.
• clean�bare�metal�surfaces�withsoap�and�water.�This�will�removeany�water-soluble�contaminants.Follow�this�with�the�use�of�waxand�grease�remover.�These�twosteps�will�ensure�a�clean�part�withno�contaminants.
• apply�a�metal�cleaner�andconversion�coating�madespecifically�for�aluminum,�ifrequired.
Module�4�-�Substrate�PreparationTextbook
Surface�Preparation�and�Masking�(REF02e) 54
Cleaning�an�aluminum�part�is�critical�for�refinishadhesion.
When�preparing�aluminum�parts�forrefinishing:
• remove�the�oxide�by�sanding�orabrading�the�surface.
• uncoated�aluminum�needs�to�berecleaned.�The�rate�that�aluminumoxidizes�varies�depending�ontemperature�and�humidity�levels.After�being�left�uncoated�for�anextended�period�of�time,�thealuminum�creates�an�aluminumoxide�coating�that�needs�to�beremoved.
Dedicated�tools�for�aluminum�only�should�be�usedwhen�working�on�aluminum�panels.
The�preparation�steps�for�a�bare�orrepaired�aluminum�part�are�similar�to�bareand�repaired�steel.
Do�not�use�the�refinish�tools�and�sandingmaterials�interchangeably�for�steel�andaluminum.�Cross�contamination�from�steelparticles�into�the�aluminum�will�causegalvanic�corrosion�to�occur.�This�willcause�premature�metal�damage�and�paintfailure.
Making�A�Sprayout�Panel
Always�compare�a�sprayout�panel�to�the�vehiclecolor.
When�creating�sprayout�panels,�thesepanels�should�be�made�to:
• show�how�the�color�will�appearfor�single-stage,�basecoat�/clearcoat,�or�multi-stage�finishes.
• duplicate�actual�sprayingconditions.
• show�the�effects�of�the�refinishtechnician’s�spraying�technique.
• aid�in�the�development�of�colorsamples.
It�may�be�beneficial�to�make�the�sprayoutpanel�when�edging�parts�to�allow�any
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Surface�Preparation�and�Masking�(REF02e) 55
color�adjustments�to�be�made�before�thevehicle�is�ready�for�exterior�refinishing.
Sprayout�panels�are�used�to�determine�color�match.
The�refinish�technician�needs�to�keep�inmind�that:
• most�paint�makers�have�speciallycoated�paper�test�panels�withblack�and�white�colors�that�areused�to�determine�when�hiding�isobtained.
• the�panel�may�require�the�use�ofa�primer�that�matches�the�colorprimer�used�on�the�vehicle.
• the�applied�color�coats�need�tomatch�the�vehicle’s�finish.
• the�proper�flash�time�needs�to�beallowed�between�application�ofrefinish�coats.
• clearcoat�needs�to�be�appliedto�the�panel�to�show�theenhancement�of�the�color.
• the�proper�dry�time�must�beallowed�between�coats�and�beforeevaluating�the�color�against�thevehicle�finish.
Specialty�Spray�Areas
Underhood�colors�can�be�a�different�color�than�theexterior�of�the�vehicle.
Underhood�and�doorjamb�colors�maybe�a�similar�or�completely�different�colorthan�the�outside�color�of�the�vehicle.These�colors�may�be�called�specialty�sprayareas.�Specialty�spray�areas�may�be�a:
• single-stage�color�used�with�aclear�binder.�The�clear�binderoffers�a�medium-�or�low-glosseffect.�This�is�used�only�whereUV�cannot�contact�the�color.Clearcoat�may�not�be�applied�to�atrunk�or�underhood�color.
• different�paint�code�that�may�ormay�not�be�listed�on�the�vehicle’slabel.
When�identifying�underhood�or�doorjambcolor,�the�information�may�be�located�ona�paint�code�label,�in�a�repair�manual,�orin�a�color�chip�book.�Computerized�paintsystems�may�also�supply�the�specialtycolors.
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Surface�Preparation�and�Masking�(REF02e) 56
When�refinishing�jambs�or�trunks,�it�may�be�easierto�mask�a�label�rather�than�remove�it�and�orderanother.
When�preparing�to�refinish�doorjambs�andtrunks:
• properly�mask�around�the�areabeing�sprayed.�This�will�aidin�reducing�or�eliminating�theamount�of�overspray�that�may�getinto�the�vehicle.
• make�the�decision�as�to�eithermask�or�remove�and�replace�theinformation�labels�that�are�locatedat�various�positions�around�thevehicle.
• replace�sound-deadening�padswith�materials�that�are�very�closeto�the�OEM�pad�color,�size,�andshape�installed�at�the�factory.
Interior�trim,�if�not�available�in�the�proper�color,�mayrequire�refinishing.
Interior�trim�typically�comes�color-matched�to�the�original�part.�Some�parts,however,�may�not�be�colored�and�mayneed�to�be�refinished.�If�refinishing�isrequired,�the�part�should�be�prepared�witha�nongloss�finish.�Interior�parts�with�a�highgloss�finish�can�cause�driving�problemswith�reflectivity�and�glare.
Interior�color�codes�can�be�found�onthe�vehicle’s�accessory�labels.�As�withpainting�exterior�plastic�parts,�adhesionpromoters�may�be�needed�when�paintinginterior�trim.
Do�not�refinish�airbag�modules.
Applying�a�finish�to�the�edges�of�a�part�allows�thesesurfaces�to�be�coated�before�it�is�installed.
Module�4�-�Substrate�PreparationTextbook
Surface�Preparation�and�Masking�(REF02e) 57
The�edges�and�backside�of�the�panels�arerefinished�to�restore�the�appearance�ofthe�vehicle�before�the�repairs.�This�taskis�generally�performed�before�the�new�orrepaired�parts�are�installed�on�a�vehicle.The�reason�this�is�done�before�installingthe�parts�is�to�aid�in�complete�coverageof�areas�that�cannot�be�easily�accessedor�protected�after�installation.�Parts�thatneed�to�be�welded�into�place�may�requirepartial�refinishing�before�they�are�installeddue�to�lack�of�access�after�installation.
Some�paint�makers�recommend�mixingclearcoat�with�the�basecoat�and�usingit�for�edging.�This�ensures�that�someof�the�clearcoat�is�applied�and�that�thedurability�to�abrasion�and�UV�protectionis�enhanced.
Module�Wrap�Up
Topics�discussed�in�this�moduleincluded:
• how�to�prepare�an�OEM�finish�forrefinishing.
• what�steps�should�be�performedto�prepare�E-coated�parts�forrefinishing.
• refinish�considerations�for�plastic,steel,�and�aluminum.
• the�importance�of�sprayout�panels.• specialty�spray�areas�and�refinish
considerations.