Paint Removal from CMU and Brick

Kenneth A. TrimberKTA-Tator, Inc.

Paint Removal from CMU and Brick - Webinar Learning Objectives

Identify SSPC/NACE, ASTM, and ICRI standards and guidelines applicable to the removal of paint from CMU and brick substrates

Describe various methods of paint removal, including advantages and disadvantages of each

Questions to Ask During Project Design

The following questions help to identify candidate coating removal methods for the project:

• Does all coating have to be removed, or just loose coating?

• If all coating must be removed, can small amounts still be permitted to remain in the porosity of the block?

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Questions to Ask During Project Design

(con’t)• Can roughening of the block or brick be

tolerated. If so, can it be heavy or only slight?

• Can large volumes of water be tolerated (environmentally and in terms of potential water intrusion into the substrate)?

• Can airborne dust be tolerated?

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Industry Standards and Guides

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Industry Standards and Guides (con’t)

• SSPC-SP13/NACE No. 6, Surface Preparation of Concrete

• SSPC-SP12/NACE No. 5, Surface Preparation and Cleaning of Metals by Water Jetting Prior to Recoating

• ICRI Guideline No. 310.2 (formerly 03732), Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays

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ICRI 310.2 – 9 Concrete Surface Profile (CSP)

Coupons

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Industry Standards and Guides (con’t)

• ASTM Standard Practices– ASTM D4258, Surface Cleaning Concrete

for Coating– ASTM D4259, Abrading Concrete– ASTM D4260, Liquid and Gelled Acid

Etching of Concrete– ASTM D4261, Surface Cleaning Concrete

Masonry Units for Coating

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Surface Preparation/Cleaning Methods in Standards/Guides

• Dry Abrasive Blast Cleaning– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4259

• Water Cleaning/Water Jetting– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4259

• Wet Abrasive Blast Cleaning– SSPC-SP13/NACE No. 6– ASTM D4259

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Surface Preparation/Cleaning Methods in Standards/Guides

(con’t)• Impact Power Tool Cleaning

– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4259

• Power Grinding/Sanding– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4259

• Scarifying/Grinding/Scabbling/Milling– ICRI Guideline No. 310.2– ASTM D4259

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Surface Preparation/Cleaning Methods in Standards/Guides

(con’t)• Acid Etching

– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4260

• Flame Cleaning– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2

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Surface Preparation/Cleaning Methods in Standards/Guides

(con’t)• Detergent Cleaning

– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4258, ASTM D4261

• Air Blast Cleaning, Water Cleaning, Steam Cleaning, Vacuum Cleaning– SSPC-SP13/NACE 6– ASTM D4258, ASTM D4261

• Chemical Stripping– Effective method of paint removal, but not addressed in the

standards/guides12

Candidate Paint Removal Methods for CMU/Brick

• Dry Abrasive Blast Cleaning• Wet Abrasive Blast Cleaning• Sodium Bicarbonate Blast Cleaning• Water Cleaning (Low Pressure <5,000 psi; High

Pressure 5000 -10,000 psi)• High Temperature Pressure Water Cleaning

(<5,000 psi)• Water Jetting (High Pressure 10,000 – 30,000 psi;

Ultra-High Pressure (>30,000 psi)• Power Tool Cleaning• Chemical Stripping

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Dry Abrasive Blast Cleaning

Abrasives propelledby compressed air

Boiler slag, copperslag, nickel slag,garnet, crushed glass,sponge, walnut shells, others

Very dusty – mayrequire containment system

Dry Abrasive Blast Cleaning (con’t)

Difficult to selectivelyremove loose coating

Elastomeric coatings canbe difficult to removedue to bounce back ofthe abrasive

Potential for very heavyroughening of thesubstrate and damageto mortar joints

Wet Abrasive Blast Cleaning

Variation of dryabrasive blastcleaning

Water is mixed with the abrasiveto control dusting

Same potential toroughen the substrate as dryabrasive blast cleaning

Wet Abrasive Blast Cleaning (con’t)

Expendable abrasive,same as dry blastcleaning

Water is mixed withabrasive using:– Water collar– Special nozzle– Special equipment

that creates a slurry

Sodium Bicarbonate Blast Cleaning

Variation of wet abrasive blast cleaning

Sodium bicarbonate (baking soda) is the abrasive

Larger particle size thanhousehold baking soda

Good for removing surface contamination,graffiti, and efflorescence

Water Cleaning Low Pressure <5,000 psi

High Pressure 5,000 to 10,000 psi

Pressure categoriesdefined in SSPC-SP12/NACE No. 5, Surface Preparation and Cleaning of Metals by Water Jetting Prior to Recoating

Despite the title, the methods suitable for CMU/brick

Water Cleaning (con’t) Low Pressure <5,000 psi

High Pressure 5,000 to 10,000 psi

Will effectively removeloose coating

Zero degree rotatingtip improves efficiency

Can remove all coatinggiven ample dwell time

Generally 5.0 to 10.0gal/min

Water Cleaning (con’t) Low Pressure <5,000 psi

High Pressure 5,000 to 10,000 psi

Potential for using largeamount of water, especially for total coatingremoval

Increased dwell time for total removal can lead to water intrusion and wetting of interior surfaces

High Temperature Low Pressure Water Cleaning

(<5,000 psi) Water temperature

250ºF and pressures <5,000 psi

High temperature improves cleaning efficiency when removing all coating.

High Temperature Low Pressure Water Cleaning

(<5,000 psi) - con’t High temperature

softens paint during removal

Water Jetting High Pressure 10,000 to 30,000 psi Ultra -High Pressure >30,000 psi

SSPC-SP12/NACE No. 5

Typically less water volume than low pressure cleaning methods

Efficiently removes existing coating

Water Jetting (con’t)High Pressure 10,000 to

30,000 psi Ultra -High Pressure >30,000

psi Integral vacuum recovery system improves housekeeping and cleanup

Water Jetting (con’t) High Pressure 10,000 to

30,000 psi Ultra -High Pressure >30,000

psi

Power Tool Cleaning

Power sanding, power grinding, needle gunning, rotopeening

Sanding and grinding remove paint with less damage to substrate than impact methods

Vacuum shrouding available

Power Tool Cleaning (con’t)

Power tool cleaning best used for localized removal

Sanding methods good for feathering

Chemical Stripping

Chemical stripping effectively removes existing paint

Biodegradable strippers are available that do not contain methylene chloride or caustic materials

Chemical Stripping – con’t

Stripper is first applied to the surface by brush, roller, or spray

Dwell time depends on coating type, temperature and thickness, but typically overnight

Chemical Stripping – con’t

Stripper and coating are removed by scraping, bucket and sponge, or pressure washing

Chemical Stripping – con’t

Depending on results, a second application may be necessary

Chemical Stripping

Second application essentially removes all coating

Original Project Design Questions

• Does all coating have to be removed, or just loose coating?

• If all coating must be removed, can small amounts still be permitted to remain in the porosity of the block?

• Can roughening of the block or brick be tolerated. If so, can it be heavy or only slight?

• Can large volumes of water be tolerated (environmentally and in terms of potential water intrusion into the substrate)?

• Can airborne dust be tolerated?

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Practical Use of Candidate Surface Preparation Methods

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1 – This table represents the practical application of the various methods when used under normal operations, but it is not absolute. For example, abrasive blast cleaning can partially remove existing coating from CMU or brick, but it is not commonly used for this purpose.2 – Roughening created by power tool cleaning is dependent on the tool being used, ranging from slight roughening with power sanding to heavy roughening with power impact tools. 3 - Slight to heavy roughening may occur. Vacuum shrouding will significantly reduce the volume of water. Without vacuum shrouding, the volume is greater, but typically not as high as pressure washing at < 10,000 psi. 4 – A large volume of water is generated if the stripper is removed by pressure washing. Much less water is involved if removed by scraping and sponge/water, but this is only practical for small localized areas.

Paint Removal Methods Extent of Coating Removal Feasible

Substrate Roughening

Extent of Paint Residue in Porosity

Volume of Water Used

Quantity of Airborne Dust

Generated

Partial Total Slight to none

Heavy Slight Mod Mod Large Little Much

Dry abrasive blast x x x none x

Wet abrasive blast x x x x x

Sodium bicarb blast x x x x none

Pressure water (<10k) x x x x none

High temp water (<5k) x x x x x none

Water jetting (>10k) x x x3 x3 x x3 x3 none

Power tool cleaning x x 2 x 2 x none x

Chemical stripping x x x x4 x4 none

Practical Use of Candidate Surface Preparation Methods

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Paint Removal Methods Extent of Coating Removal Feasible

Partial TotalDry abrasive blast xWet abrasive blast xSodium bicarbonate blast xPressure water (<10k) xHigh temp water (<5k) x x

Water jetting (>10k) x xPower tool cleaning xChemical stripping x

Practical Use of Candidate Surface Preparation Methods

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2 – Roughening created by power tool cleaning is dependent on the tool being used, ranging from slight roughening with power sanding to heavy roughening with power impact tools.

3 – Slight to heavy roughening may occur

Paint Removal Methods Substrate Roughening

Slight to none

Heavy

Dry abrasive blast x

Wet abrasive blast x

Sodium bicarbonate blast x

Pressure water (<10k) x

High temp water (<5k) x

Water jetting (>10k) x3 x3

Power tool cleaning x 2 x 2

Chemical stripping x

Practical Use of Candidate Surface Preparation Methods

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Paint Removal Methods Extent of Paint Residue in Porosity

Slight Mod

Dry abrasive blast x

Wet abrasive blast x

Sodium bicarbonate blast x

Pressure water (<10k) x

High temp water (<5k) x

Water jetting (>10k) x

Power tool cleaning x

Chemical stripping x

Practical Use of Candidate Surface Preparation Methods

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3 – Vacuum shrouding will significantly reduce the volume of water. Without vacuum shrouding, the volume is greater, but typically not as high as pressure washing at < 10,000 psi.

4 – A large volume of water is generated if the stripper is removed by pressure washing. Much less water is involved if removed by scraping and sponge/water, but this is only practical for small localized areas.

Paint Removal Methods Volume of Water Used

Mod Large

Dry abrasive blast none

Wet abrasive blast x

Sodium bicarbonate blast x

Pressure water (<10k) x

High temp water (<5k) x

Water jetting (>10k) x3 x3

Power tool cleaning none

Chemical stripping x4 x4

Practical Use of Candidate Surface Preparation Methods

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Paint Removal Methods Quantity of Airborne Dust

Generated

Little Much

Dry abrasive blast x

Wet abrasive blast x

Sodium bicarbonate blast none

Pressure water (<10k) none

High temp water (<5k) none

Water jetting (>10k) none

Power tool cleaning x

Chemical stripping none

Productivity

Production rates for some of the methods can be found in:– Painting and Decorating Contractors of America (PDCA)

Estimating Guide, Volume 2, Rates and Tableswww.PDCA .org (314-514-7322)

– ICRI Guideline No. 310.2 (formerly 03732), Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlayswww.icri.org (847-827-0830)

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Additional Information

• Paper associated with the webinar to be published in Durability + Design daily e-news - week of November 1, 2010

• SSPC 2011 – One day seminar on commercial painting – problems with painting CMU, surface preparation, application, and paint systems Feb 1, 2001

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Paint Removal from Masonry Substrates Webinar -

Questions