aga - a guide to specifying and inspecting hot-dipped galvanized steel

8/14/2019 AGA - A Guide to Specifying and Inspecting Hot-dipped Galvanized Steel

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HOT-DIPGALVANIZING FORCORROSIONPREVENTION:

A guide to specifying & inspecting

hot -dip galvanized reinforcing steel

HOT-DIPGALVANIZING FORCORROSIONPREVENTION:

A guide to specifying & inspect ing

hot-dip galvanized reinforcing steel


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TABLE OF CONTENTSCORROSION PROTECTION FOR STEEL 2

Steel Corrosion 2How Zinc Prevents Steel from Corrosion 4

Barrier Protection 4Cathodic Protection 4

DESIGN, FABRICATION & INSTALLATION 5Design 5

Steel Selection 6Detailing Reinforcement 6Dissimiliar Metals in Concrete 6

Fabrication 6Bending Parts 6Storage & Handling 6

Installation 7Welding 7Local Repair of Coating 7Removal of Forms 7

THE HOT-DIP GALVANIZING PROCESS 7Surface Preparation 7Galvanizing 8

PHYSICAL PROPERTIES OF HOT-DIP GALVANIZED COATINGS 9The Metallurgical Bond 9

Impact & Abrasion Resistance 9Corner & Edge Protection 9Complete Coating 10

MECHANICAL PROPERTIES OF GALVANIZED STEEL 10Ductibility & Yield/Tensile Strength 10Fatigue Strength 10Bond Strength 10Zinc Reaction in Concrete 11

INSPECTION 11Coating Thickness 12

Magnetic Thickness Measurements 12Stripping Method 13Weighing Bars Before and After Galvanizing 13Microscopy 13Sampling Statistics 13

Factors Affecting Coating Thickness 13Coating Appearance 14Visual Guide 14

Bare Spots 14Dross Protrusions 15Blisters & Slivers 15Lumps & Runs 15Flux Inclusions 15Ash Inclusions 15Gray or Mottled Coating Appearance 15

Brown Staining 15Rust Staining 16Wet Storage Stain 16

Galvanized Reinforcing Steel Testing 16Bond Strength Test 16Chromate Finish Test 16Embrittlement Test 16Accelerated Aging Test 16

FIELD PERFORMANCE OF GALVANIZED REINFORCEMENT 17Vertical Construction 17Horizontal Construction 18

ADDITIONAL RESOURCES 19ASTM & CSA SPECIFICATIONS 20


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CORROSIONPROTECTION FORSTEEL

Repairing damage caused by corrosion is amulti-billion dollar problem. Observations ofnumerous structures show that corrosion ofreinforcing steel is either a prime factor, or atleast an important factor, contributing to stain-ing, cracking and/or spalling of concrete struc-tures. The effects of corrosion often requirecostly repairs and continued maintenance dur-ing the structures life.

When steel is exposed to an aggressiveenvironment, or if the design details or work-manship are inadequate, corrosion of the rein-

forcement may become excessive, and the con-crete may exhibit signs of distress.

Galvanized reinforcing steel is effectivelyand economically used in concrete where unpro-tected reinforcement will not have adequatedurability. The susceptibility of concrete struc-tures to the intrusion of chlorides is the primaryincentive for using galvanized steel reinforce-ment. Galvanized reinforcing steel is especiallyuseful when the reinforcement will be exposed

to the weather before construction begins.Galvanizing provides visible assurance that thesteel has not rusted.

This publication provides information ondesign variables involved in specifying galva-nized reinforcement. This publication also pro-

vides details on the specification and practicesinvolved with galvanized reinforcement, as wellas inspection details.

STEEL CORROSIONRust, irons corrosion product, is the resultof an electrochemical process. Rust occursbecause of differences in electrical potentialbetween small areas on the steel surface involv-ing anodes, cathodes and an electrolyte (a medi-um for conducting ions). These differences inpotential on the steel surface are caused by vari-ations in steel composition/structure, the pres-ence of impurities, uneven internal stress,and/or corrosive environments.

In the presence of an electrolyte, the differ-ences mentioned above create corrosion cells,which consist of microscopic anodes and cath-odes. Because of differences in potential withinthe cell, negatively charged electrons flow fromanode to cathode, and iron atoms in the anodearea are converted to posi-tively charge iron ions.The positively charged

iron ions (FE+ +

) of theanode attract and reactwith the negatively chargedhydroxyl ions (OH-) inthe electrolyte to form ironoxide, or rust. Negativelycharged electrons (e-) react at the cathodesurface with positively charged hydrogen ions(H+ ) in the electrolyte to form hydrogen gas.A simplified picture of what occurs in thiscorrosion cell is shown in Figure 1.

Corrosion of unprotected reinforcing steel

creates hazard due t o spal l ing concrete.

Galvanizing rebar helps prevent corrosion.

FIGURE 1 - Corrosion Cell

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Impurities present in the electrolyte createan even better conductive path for the corrosionprocess. For example, these impurities can bethe constituents in which the steel is immersedor present in atmospheric contaminants, includ-ing sulfur oxides, chlorides or other pollutantspresent in damp atmospheres or dissolved insurface moisture. Calcium hydroxide, present in

hardened concrete, also acts as an electrolyte inthe presence of moisture.

Under normal conditions, concrete is alka-line (pH of about 12.5) due to the presence ofcalcium hydroxide. In such an environment, apassivating iron-oxide film forms on the steel,causing almost complete corrosion inhibition.As the pH of the concrete surrounding the rein-forcement is reduced by the intrusion of salts,

leaching or carbonation, the system becomesactive and corrosion proceeds.

The presence of chloride ions can affect theinhibitive properties of the concrete in twoways. The presence of chloride ions creates lat-tice vacancies in the oxide film, thus providingdefects in the film through which metal ionsmay migrate more rapidly and permit pittingcorrosion to proceed. Also, if the hydroxyl ionconcentration is reduced, for example by car-

bonation, the pH is lowered and the corrosionproceeds further. In the presence of oxygen,

inhibition of iron corrosion occurs at a pH of12.0. But as the pH is reduced, the corrosionrate increases. With reduction of pH to 11.5,the iron corrosion rate increases by as much asfive times the rate at a pH of 12.0.

At an active anodic site, particularly in pits,the formation of positively charged ferrous ions

attracts negatively charged chloride ions, givinghigh concentrations of ferrous chloride. Ferrouschloride partially hydrolyzes, yielding hydrochlo-ric acid and an acid reaction. These reactionsreduce protection at the steel-concrete inter-face. At a corroding surface, the pH may be 6.0or less.

As mentioned before, the anode and cath-ode areas on a piece of steel are microscopic.

Greatly magnified, the surface might appear asthe mosaic of anodes and cathodes pictured inFigure 2, all electrically connected by the under-lying steel.

Moisture in the concrete provides the elec-trolyte and completes the electrical pathbetween the anodes and cathodes on the metalsurface. Due to potential differences, a smallelectric current begins to flow as the metal isconsumed in the anodic area. The iron ions pro-

duced at the anode combine with the environ-ment to form the loose, flaky iron oxide knownas rust.

As anodic areas corrode,new material of different

composition and structureis exposed. This resultsin a change of electricalpotentials and alsochanges the location of

anodic and cathodic sites.The shifting of anodic and

cathodic sites does not occurall at once. In time, previously

uncorroded areas are attacked, and a uni-form surface corrosion is produced. Thisprocess continues until the steel is entirely con-sumed.

FIGURE 2 - Corr osion of Steel1. Corrosion of steel is an electro-chemical reaction. Minute differ-ences in structure of the steelschemisty create a mosaic pat-tern of anodes and cathodescontaining stored electrochemi-

cal energy.2. Moisture forms an electrolyte,which completes the elctrical pathbetween anodes and cathodes,spontaneously releasing the storedelectrochemical energy. A small electricalcurrent beings to flow, carrying away particlesof the anode areas. The particle combines with theenvironment to form rust. When salt or acid is added tothe moisture, the flow of electric current and corrosionaccelerates.3. At this stage, the anodes are corroded and cathodes areprotected. However, the instability of the metal itself caus-es the anodes to change to cathodes and the corrosioncycle beings again, resulting in uniform corrosion of theentire surface.

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The corrosion products that form on steelhave much greater volume than the metal that isconsumed in the corrosion reaction. Thisincrease in volume around the bare steel rebarexerts great disruptive tensile stress on the sur-rounding concrete. When resultant tensilestress is greater than the concrete tensilestrength, the concrete cracks (Figure 3), leading

to further corrosion. Corrosion cracks are usual-ly parallel to the reinforcement and are quitedistinct from transverse cracks associated withtension in the reinforcement caused by loading.As the corrosion proceeds, the longitudinalcracks widen and, together with structural trans-verse cracks, cause spalling of the concrete.

HOW ZINC PREVENTS STEELFROM CORRODING

The reason for the extensive use of hot-dip

galvanized steel is the twofold nature of thecoating. As a barrier coating, galvanizing pro-vides a tough, metallurgically bonded zinc coat-ing that completely covers the steel surface andseals the steel from the environments corrosiveaction. Additionally, zincs sacrificial action(cathodic) protects the steel even where damageor minor discontinuity occur in the coating.

It should be noted that the performance ofhot-dip galvanized reinforcing steel in concreteis quite different than that of hot-dip galvanizedsteel in atmospheric conditions.

Barrier ProtectionZinc is characterized by its amphoteric

nature and its ability to passivate due to the for-mation of protective reaction product films.Reaction of zinc with fresh cement leads to pas-sivity by formation of a diffusion barrier layer ofzinc corrosion products.

Comparison of the two lines in Figure 4emphasizes the importance of the passivatinglayer for corrosion protection against chlorides.

Cathodic ProtectionTable 1, page 5, shows the galvanic series

of metals and alloys arranged in decreasingorder of electrical activity. Metals toward thetop of the table, often referred to as lessnoble metals, have a greater tendency to loseelectrons than the more noble metals at the bot-tom of the table. Thus, metals higher in the

series provide cathodic (or sacrificial) protectionto those metals below them.

Because zinc is anodic to steel, the galva-nized coating provides cathodic protection toexposed steel. When zinc and steel are connect-ed in the presence of an electrolyte, the zinc isslowly consumed, while the steel is protected.Zincs sacrificial action offers protection wheresmall areas of steel are exposed, such as cutedges, drill-holes, scratches, or as the result ofsevere surface abrasion. Cathodic protection ofthe steel from corrosion continues until all thezinc in the immediate area is consumed.

Both steel and chromated zinc are normallypassive in the highly alkaline environment ofconcrete. However, penetration of chloride ionsto the metal surface can break down this passiv-ity and initiate rusting of steel or sacrificial cor-

FIGURE 3 - Spall ing Concrete

Effect of Chloride Concentration on the CriticalPitting Potential (Duval)

Zinc

Zinc Passivated byCa(OH)2 for 15 days

0

-200

-400

-600

-800

-1000

-1200

10-2 10-1 1Concentration of Cl-(N)

mV(SCE)

FIGURE 4 - Zincs Passivation Quali ty

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rosion of the zinc. The susceptibility of con-crete structures to the intrusion of chlorides isthe primary incentive for using galvanized steelreinforcement.Galvanized reinforcing steel can withstand

exposure to chloride ion concentrations severaltimes higher (at least 4 to 5 times) than thechloride level that causes corrosion in blacksteel reinforcement. While black steel in con-crete typically depassivates below a pH of 11.5,galvanized reinforcement can remain passivatedat a lower pH, thereby offering substantial pro-tection against the effects of concrete carbona-tion.

These two factors combined -- chloride tol-erance and carbonation resistance -- are widelyaccepted as the basis for superior performanceof galvanized reinforcement compared to blacksteel reinforcement. The total life of a galva-nized coating in concrete is made up of the timetaken for the zinc to depassivate (which islonger than that for black steel, because of itshigher tolerance to chloride ions and carbona-tion resistance), plus the time taken for the dis-

solution of the alloy layers in the zinc coating.Only after the coating has fully dissolved in aregion of the bar will localized corrosion of thesteel begin.

Galvanizing protects the steel during in-plant and on-site storage, as well as afterembedment in the concrete. In areas where the

reinforcement may be exposed due to thin orporous concrete, cracking, or damage to theconcrete, the galvanized coating providesextended protection. Since zinc corrosion prod-ucts occupy a smaller volume than iron corro-sion products, the corrosion that may occur tothe galvanized coating causes little or no disrup-tion to the surrounding concrete. Tests alsoconfirm that zinc corrosion products are pow-dery, non-adherent and capable of migrating

from the surface of the galvanized reinforce-ment into the concrete matrix, reducing thelikelihood of zinc corrosion-induced spalling ofthe concrete (Yeomans).

DESIGN,FABRICATION &INSTALLATIONDESIGN

When galvanized steel is specified (seeAmerican Galvanizers Associations publicationSuggested Specification for Hot-Dip GalvanizingReinforcing Steel), the design requirements andinstallation procedures employed should be noless stringent than for structures where uncoat-ed steel reinforcement is used. In addition,there are some special requirements to beobserved when galvanized steel is used. The fol-

lowing suggestions are intended as a guide fordesigners, engineers, contractors and inspec-tors. They are intended as a supplement toother codes and standards dealing with design,fabrication and construction of reinforced con-crete structures, and deal only with those spe-cial considerations that arise due to the use ofgalvanized steel.

CORRODED ENDAnopdic or less noble

(Electronegative)

MagnesiumZinc

AluminumCadmium

Iron or Steel

Stainless Steels (active)Soft Solders

LeadTin

NickelBrass

BronzesCopper

Nickel-Copper AlloysStainless Steels (passive)

Silver SolderSilver

GoldPlatinum

PROTECTED ENDCathodic or more noble

(Electropositive)

Arrangement ofMetals in t he

Galvanic Series:

Any one of these

metals and alloys willtheoretically corrode

while offering pro-tection to any other

which is lower in theseries, so long as

both are electricallyconnected.

In actual practice,

however, zinc is byfar the most effec-

tive in this respect.

TABLE 1 - Galvanic Series of Metals


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Steel SelectionThe concrete reinforcing steel to be galva-

nized shall conform to one of the followingASTM specifications: A 615, A 616, A 617 or A706 (see page 20).

Detailing of ReinforcementDetailing of galvanized reinforcing steel

should conform to the design specifications foruncoated steel bars and to normal standardpractice consistent with the recommendationsof the Concrete Reinforcing Steel Institute(CRSI).

Overlapping lengths of hot-dip galvanizedreinforcing steel are identical to uncoated steelreinforcement overlap lengths because of the

equivalent bond strength to concrete.

Dissimilar Metals in ConcreteAnother consideration when using galva-

nized reinforcement in concrete is the possibili-ty of establishing a bimetallic couple betweenzinc and bare steel (i.e. at a break in the zinccoating or direct contact between galvanizedsteel and black steel bars) or other dissimilarmetals. A bimetallic couple of this type in con-

crete should not be expected to exhibit corro-sive reactions as long as the two metals remainpassivated. To ensure this is the case, the con-crete depth to the zinc/steel contact should notbe less than the cover required to protect blacksteel alone under the same conditions.

Therefore, when galvanized reinforcementis used in concrete, it should not be coupleddirectly to large areas of black steel reinforce-ment, copper or other dissimilar metal. Bar sup-

ports and accessories should be galvanized. Tiewire should be annealed wire, 16-gauge or heav-ier, preferably galvanized. If desired, polyethyl-ene and other similar tapes can be used to pro-vide insulation between dissimilar metals.

FABRICATION

Bending BarsHooks or bends should be smooth and not

sharp. Cold-bending should be in accordancewith the recommendations of CRSI. When barsare bent cold prior to galvanizing, they need tobe fabricated to a bend diameter equal to or

greater than those specified in Table 2. Materialcan be cold bent tighter than shown in Table 3 ifit is stress-relieved at a temperature from 900to 1050 F (482-566 C) for one hour per inch(2.5 cm) of bar diameter before hot-dip galvaniz-ing.

When galvanizing is performed beforebending, some cracking and flaking of the galva-nized coating at the bend may occur. The speedat which the article is bent also may affect coat-ing integrity. The galvanized coating is bestmaintained at slower bend speeds. According to

ASTM A 767 (see page 20), some cracking andflaking of the galvanized coating in the bend areais not cause for rejection. Any flaking or crackingcan be repaired as described in ASTM A 780 (seepage 20).

Storage &Handling

Galvanized barsmay be stored outdoors

with no corrosion per-formance degradation.Their general ease ofstorage makes it feasi-ble to store standardlengths so that they areavailable on demand.Another important char-acteristic of galvanizedreinforcing steel is that it

Minimum Fini shed Bend Diameters-Inch-Pound Unit sBar No. Grade 40 Grade 50 Grade 60 Grade 75

3, 4, 5, 6 6d 6d 6d -- -

7, 8 6d 8d 8d -- -

9, 10 8d 8d 8d -- -

11 8d 8d 8d 8d

14, 18 --- --- 10d 10d

d= nominal diameter of the bar

TABLE 2 - Minimum Bend Diameters Suggested

Standard-size rein-forcing steel, bothstraight and fabri-cated, can be galva-nized in advance andeasily stored untilneeded.

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can be handled and placed in the same manneras black steel reinforcement, because of thegreat abrasion resistance of galvanized steel.(For additional information, see AmericanGalvanizers Associations Field Handling Guide:Hot-Dip Galvanizing vs. Fusion Bonded Epoxy.)

INSTALLATIONWelding

Welding galvanized reinforcement shouldconform to the requirements of the current edi-tion of the American Welding Society (AWS)Standard Practice AWS D19.0, Welding Zinc-Coated Steel. Welding of galvanized reinforce-ment poses no problems, provided adequateprecautions are taken. These include a slower

welding rate and proper ventilation. The ventila-tion normally required for welding operations isconsidered adequate.

Local Repair of CoatingLocal removal of the galvanized coating in

the area of welds, bends, or sheared ends willnot significantly affect the protection offered bygalvanizing, provided the exposed surface areais small compared to the adjacent surface areaof galvanized steel. When the exposed area isexcessive and gaps are evident in the galva-nized coating, the area can be repaired in accor-dance with ASTM A 780 (see page 20).

Removal of FormsBecause cements with naturally low occur-

ring levels of chromates may react with zinc andretard hardening and initial set, it is importantto ensure that forms and supports are notremoved before the concrete has developed therequired strength to support itself. Normal form

removal practices may be utilized if the cementcontains at least 100 ppm of chromates in thefinal concrete mix or if the hot-dip galvanizedbars are chromate-passivated according to ASTMA 767 (see page 20), Section 4.3.

THE HOT-DIPGALVANIZING

PROCESSThe hot-dip galvanizing process consists ofthree basic steps: surface preparation, galvaniz-ing and inspection. Each of these steps is impor-tant in obtaining a quality galvanized coating(Figure 5).

SURFACE PREPARATIONIt is essential for the steel surface to be

clean and uncontaminated in order to obtain a

uniform, adherent coating. Surface preparationis usually performed in sequence by caustic(alkaline) cleaning, water rinsing, pickling, a sec-ond water rinsing and fluxing.

The caustic cleaner removes organic con-taminants including dirt, water-based paintmarkings, grease and oil. Next, scale and rustare removed by a pickling bath of hot sulfuricacid (150 F / 66 C) or room temperature

hydrochloric acid. Water rinsing usually followsboth caustic cleaning and pickling.

Surface preparation can also be accom-plished using abrasive cleaning as an alternateto, or in conjunction with, chemical cleaning.Abrasive cleaning is a mechanical process inwhich shot or grit is propelled against the mate-rial by air blasts or rapidly rotating wheels.

The abrasion-resistant galvanizedcoating requires no special han-

dling procedures.


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The final cleaning of the steel is performedby a flux, an aqueous solution of zinc ammoni-um chloride that prevents any oxidation of thenewly cleaned steel and promotes good zincadhesion to the steel.

GALVANIZINGThe material to be coated is immersed in a

bath of molten zinc maintained at temperaturesof more than 800 F (430 C). A typical bathchemistry used in hot-dip galvanizing is 98%pure zinc. The time of immersion in the galva-nizing bath varies depending on the dimensionsand chemistry of the material being coated.Materials with thinner sections galvanize morequickly than those with thicker sections.

Surface appearance and coating thicknessare the result of many process parameters.Some of these parameters are steel chemistry;variations in immersion time and/or bath tem-perature; rate of withdrawal from the galvaniz-ing bath; removal of excess zinc by wiping, shak-ing or centrifuging; and control of the coolingrate by water quenching or air cooling.

The American Galvanizers Association has

developed procedures for galvanizing reinforc-ing steel to assure the galvanized coating willmeet not only the minimum coating weights forgalvanized reinforcement specified in ASTM A767 (see page 20) as seen here in Table 4, butalso the other requirements of the standard.

Rebar being removed fr om the bathof molten zinc. Excess zinc runs offthe bars, but enough zinc has bond-ed to the steel to protect it fromcorrosion for decades.

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Surface Preparation Galvanizing Inspection

CausticCleaning

Rinsing PicklingRinsing Flux

Solution

Molten

Zinc Bath

Cooling andQuality Assurance

FIGURE 5 - The Hot-Dip Galvanizing Process

Because of galvanizings unique, tough coating,

there is no tip-toeing around the work-site. The

intermetall ic layers of galvanized coating areharder than the base steel, so galvanized rebar

is extremely resistant to damage from abrasion

and other installation elements.


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PHYSICALPROPERTIES OFHOT-DIPGALVANIZEDCOATINGS

METALLURGICAL BONDHot-dip galvanizing is a factory-applied

coating that provides a combination of proper-ties unmatched by other coating systemsbecause of its unique metallurgical bond withthe steel.

The photomicrograph in Figure 6 shows asection of a typical hot-dip galvanized coating.

The galvanized coating consists of a progressionof zinc-iron alloy layers metallurgically bondedto the base steel. The metallurgical bondformed by the galvanizing process ensures thatno underfilm corrosion can occur. Epoxy coat-ings, on the other hand, merely overcoat thesteel with a penetrable film. As il lustrated inFigure 7, once the epoxy film is broken and thebare steel is exposed, corrosion begins as if noprotection existed.

IMPACT & ABRASION

RESISTANCEThe ductile outer zinc layer provides good

impact resistance to the bonded galvanizedcoating. The photomicrograph in Figure 6 showsthe typical hardness values of a hot-dip galva-nized coating. The hardness of the zeta, gamma

and delta layers is actually greater than the basesteels and provides exceptional resistance tocoating damage from abrasion.

CORNER & EDGEPROTECTION

Corrosion oftenbegins at corners oredges of products thathave not been galva-nized. Epoxy coatings,regardless of applicationmethod, are thinnest atsuch places. The galva-nized coating will be atleast as thick, possibly thicker, on corners andedges as on the general surface. This providesequal or extra protection to these critical areas(see Figure 8).

FIGURE 6 - TypicalZinc-Iron AlloyLayers

Eta(100% Zn)

70 DPN

Zeta(94% Zn, 6% Fe)

180 DPN

Delta(90% Zn, 10% Fe)

245 DPN

Gamma(75% Zn, 25% Fe)

250 DPN

Steel(100% Fe)159 DPN

FIGURE 7 - Barri er Prot ect ion Onl y

This is whathappens at ascratch ongalvanized steel.The zinc coati ngsacrifices itselfslowly to prot ectthe steel. This sac-rifi cial action con-tinues as long asthere is zinc in theimmediate area.

This is whathappens at ascratch on paintedsteel. The exposedsteel corrodes,forms a pocket ofrust, and lifts thepaint film from themetal surface toform a blister. Thisblister will continueto grow.

This is whathappens at ascratch on steelcoated with a lessactive metal, suchas copper. Theexposed st eelcorrodes fasterthan normal toprotect the morenoble metal,copper.

FIGURE 8 - Ful l CornerProtection

DPN = Diamond Pyramid Number


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COMPLETE COATINGBecause galvanizing is accomplished

through total immersion, all surfaces of the arti-cle are fully coated and protected, includingareas inaccessible and hard to reach with brush-or spray-applied coatings. Additionally, theintegrity of any galvanized coating is ensured

because zinc will not metallurgically bond tounclean steel. Thus, any uncoated area is imme-diately apparent as the work is withdrawn fromthe molten zinc. Adjustments are made on thespot, when required, so a fully protected item isdelivered to the job site.

MECHANICAL

PROPERTIESOF HOT-DIPGALVANIZED STEEL

DUCTILITY & YIELD/TENSILESTRENGTH

Ductility and strength ofreinforcing steel are important

to prevent brittle failure of rein-forced concrete. Studies of theeffect of galvanizing on themechanical properties of steelreinforcing bars have demon-strated that the tensile, yield andultimate strength, ultimate elon-gation, and bend requirementsof steel reinforcement are sub-stantially unaffected by hot-dipgalvanizing, provided proper

attention is given to steel selec-tion, fabrication practices andgalvanizing procedures.

The effect of the galvanizing process on theductility of steel bar anchors and inserts afterbeing subjected to different fabrication proce-dures also has been investigated. The resultsdemonstrate conclusively that, with correctchoice of steel and galvanizing procedures,there is no reduction in the steels ductility.

FATIGUE STRENGTHAn extensive experimental program exam-

ining the fatigue resistance of galvanized steelreinforcement shows that deformed reinforcingsteel, exposed to an aggressive environmentprior to testing under cyclic tension loading,perform better when galvanized.

BOND STRENGTHGood bonding between reinforcing steel

and concrete is essential for reliable perform-ance of reinforced concrete structures. Whenprotective coatings on steel are used, it is essen-tial to ensure that these coatings do not reducebond strength. Studies of the bonding of galva-nized and black steel bars to Portland Cement

Source: University of California, Berkeley

Concrete-Reinforcing Steel Bond

Study A Study B Study C1000

800

600

400

200

1 3 12 1 3 121 3 12Months of Curing

Stress

in

Pou

nds-Per-Square-Inch

Black SteelGalvanized

TABLE 3 - Bond Between Concrete and Reinforcing Steel

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concrete have been investigated. The results ofthese studies indicate:

1. Development of the bond between steeland concrete depends on age and environment.

2. In some cases, the time required fordeveloping full bond-strength between steel and

concrete may be greater for galvanized barsthan for black, depending on the zincate/cementreaction.

3. The fully developed bond strength ofgalvanized and black deformed bars is the same.In Table 3, the bond strength of galvanized barsis greater than for similar black bars.

ZINC REACTION IN

CONCRETEDuring curing, the galvanized surface of

steel reinforce-ment reactswith the alka-line cementpaste to formstable, insolu-ble zinc saltsaccompanied

by hydrogenevolution.This has raisedthe concern ofthe possibilityof steelembrittlementdue to hydro-gen absorp-tion.

Laboratory studies indicate that this liberatedhydrogen does not permeate the galvanizedcoating to the underlying steel and the reactionceases as soon as the concrete hardens.

Reaction of zincates with fresh PortlandCement mortar may retard set and earlystrength development, but later, setting occurscompletely with no detrimental effects on theconcrete. In fact, an increase in bond strengthoccurs.

Most typesof cement andmany aggre-gates containsmall quanti tiesof chromates.These chro-mates passivate

the zinc surface,minimizing theevolution ofhydrogen duringthe reaction between zinc and the concrete. Ifthe cement and aggregate contain less chromatethan will yield at least 100 ppm in the final con-crete mix, the galvanized bars can be dipped ina chromate solution or chromates can be addedto the water when the concrete is mixed.

INSPECTIONOnce the reinforcing steel has been galva-

nized, the product must be inspected to ensurecompliance with specification requirements.

The standard specification for hot-dip gal-vanized reinforcing steel is ASTM A 767 (seepage 20). This specification covers individual

bars, as well as groups of bars. When the barsare fabricated into assemblies prior to galvaniz-ing, the standard specification for hot-dipgalvanized assemblies, ASTM A 123 (see page 20)applies. In Canada, for either bars or assemblies,the standard specification for hot-dip galvanizedart icles is CSA G 164 (see page 20).

Inspection of the hot-dip galvanized prod-uct, as the final step in the galvanizing process,can be most effectively and efficiently conduct-ed at the galvanizers plant. Here, questions canbe raised and answered quickly, inspectionspeeded up and time saved, which is turned intoan asset for the overall project.

Because ofthe bondstrengthbetween gal-vanized steeland concrete,galvanizedrebar is used

successfullyin a variety ofapplicationsto providereliable cor-

rosion prevention. The concretein the photo to the left was inservice for almost 20 years in asalt-wat er, marine environmentand required jackhammering tobreak the bond between it andthe galvanized rebar.

At a const ruct ion sit e, galva-

nized, fabricated rebar hasbeen installed and is ready for

concrete to be placed.


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COATING THICKNESSThe thickness of the galvanized coating is

the primary factor in determining the servicelife of the product. The thicker the coating, thelonger it provides corrosion protection. Forsteel embedded in concrete, the relationship isapproximately linear. For example, the service

life is doubled or tripled if the weight of thezinc coating is doubled or tripled.

The minimum coating thickness require-ments for reinforcing bars from ASTM A 767 (seepage 20) are summarized in Table 4. The conver-sion of these weights into thickness values isshown in Table 5. The minimum coating thicknessrequirements for reinforcing bar assemblies fromASTM A 123 (see page 20) are summarized inTable 6. The conversion of these grades into thick-

ness and weight numbers is shown on Table 7.

The galvanized coating thickness can bedetermined via several methods. The size, shapeand number of parts to be tested likely dictatesthe method of testing. Some test methods are

non-destructive,while others requireremoval of the zinccoating or sectioning

of the test article,thereby destroyingthe test article.

Magnetic Thickness Measurements - Thethickness of the coating can be determined bymagnetic thickness gauge measurements inaccordance with ASTM E 376 (see page 20). Tofind the specimen coating thickness, a minimumof five randomly located readings must be takento represent, as much as practical, the entire

surface area of the bar. After specimen coatingthicknesses have been determined for threebars, the average of those three bars is the aver-age coating thickness for the size lot. If the lotsize is increased, more than three samples maybe needed.

oat ing Class Weight of Zinc Coat ingass I

Bar Designat ion Size No. 3 915 (3.00)Bar Designat ion Size No. 4 & larger 1070 (3.50)

ass IIBar Designation Size No. 3 & larger 610 (2.00)

ABLE 4 - ASTM A 767 COATINGHICKNESS REQUIREMENTSoat ing Class Mass of Zinc Coat ing

min, oz/ft2 of Surface

oz/ft2 gm/m2 mils microns

1.00 305.2 1.70 431.50 457.8 2.55 652.00 610.3 3.40 862.50 762.9 4.25 1083.00 915.5 5.10 1303.50 1068.1 5.95 153

BLE 5 - CONVERSION FROM ZINC COATING WEIGHTO ZINC COATING THICKNESS

Coat ing Wei ght Coat ing Thickness

ucturalpes 45 65 75 85 100

p 45 65 75 75 100e & Tubing 45 45 75 75 75

e 35 50 60 65 80

terial All Specimens Testedegory Steel Thickness Measurement in inches (mm)

< 1/16 (< 1.6)1/16 to 3/16 to 4.8 to < 6.4) >-1/4 (>- 6.4)

BLE 6 - ASTM A 123 COATINGCKNESS REQUIREMENTS

im um Average Coat ing Thickness Grade by Materi al Category

BLE 7 - ASTM A 123 COATINGCKNESS REQUIREMENTS

5 1.4 0.8 35 2455 1.8 1.0 45 320

0 2.0 1.2 50 3555 2.2 1.3 55 390

0 2.4 1.4 60 4255 2.6 1.5 65 4605 3.0 1.7 75 530

0 3.1 1.9 80 5655 3.3 2.0 85 600

00 3.9 2.3 100 705

atingade mils oz/ft 2 m g/m

mum Coating Thickness by Grade*

nversions in thi s table are based on the met ric t hickness value equivalentsthe next earlier version of this specification, using conversion factors con-

nt with Table x.21 in ASTM A 653 (see page 20), rounded to the nearestx 0.03937; oz/ft2 = m x 0.02316; g/m2 = m x 7.067.

2


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Stripping Method - The average coatingweight can be determined by stripping speci-mens taken from sample bars in accordancewith ASTM A 90 (see page 20). Cut one speci-men from each end of the bar and a third speci-men from the center of the bar. The averagecoating weight for the bar is derived from theaverages of the specimen coating weights

obtained for each of the three pieces. Thismethod is a destructive test and is not appropri-ate for assemblies of reinforcing steel.

Weighing Bars Before & After Galvanizing -The average coating weight can be determinedby weighing the bars before and after galvaniz-ing. The first weight is determined after picklingand drying, the second after the hot-dip galva-nized bar has cooled to an ambient temperature.

The coating weight is the difference between thetwo weights divided by the surface area of thebar. This method does not take into account theweight of iron reacted from the bar that is incor-porated into the coating, so the coating weightcan be underestimated by as much as 10%. Basemetal reactivity affects the extent of underesti-mation. This method is only appropriate forassemblies if the surface area of the assemblycan be obtained.

Microscopy - The average coating weight canbe determined using cross-sectioned samplesand optical microscopy in accordance withASTM B 487 (see page 20). The thickness of across-sectioned sample is determined by opticalmeasurement. The average coating thickness isobtained by averaging five thickness measure-ments on widely dispersed cross-sections alongthe length of the bars, so as to represent theentire surface of the bar. The average coatingthickness must then be converted to coatingweight. This test method is destructive and isnot appropriate for assemblies of reinforcingsteel.

Sampling Statistics - For determining theaverage coating weight, three random samplesmust be tested from each lot. A lot is definedas all bars of one size furnished to the samehot-rolled reinforcing bar specifications thathave been galvanized within a single productionshift. It is essential for selected specimens to berepresentative of the inspection lot. Because

inspection lot sizes can be very small, statisticalsampling plans, such as those covered in ASTMB 602 (see page 20), may not be valid. However,such a statistical sampling plan is recommendedfor large lots.

FACTORS AFFECTING

COATING THICKNESSThere are several factors that affect the

coating thickness. The only two that are readilymanageable by the galvanizer are the tempera-ture of the zinc bath and the withdrawal rate ofthe reinforcing bar from the zinc bath. To a less-er degree, the roughness of the surface affectsthe coating thickness. Therefore, parts that havebeen over-pickled and are rough on the surfacecan develop thicker zinc-iron layers.

There are two conditions that are uncon-trollable by the galvanizer that significantlyaffect the outcome of the finished galvanizedcoating. The first is the silicon and phosphorouscontent of the reinforcing steel. Certain levels ofsilicon and phosphorous tend to accelerate thegrowth of the zinc-iron alloy layers so that thecoating continues to grow for the entire timethe reinforcing steel is immersed in the zincbath. The Sandelin Curve (Figure 9 on the nextpage) shows the coating thickness produced bysteels with different silicon levels by immersing

them in zinc baths for the same amount of time.There are two regions where the coating canbecome very thick, between 0.05%and 0.14%,and over .25%, silicon. The growth of coatings inthese two regions of silicon concentration pro-duces very thick, and thereby brittle, coatingscharacterized by a matte gray surface, indicatinga predominately zinc-iron intermetallic coatingwith little or no free-zinc outer layer.


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Hot-dip galvanized coatings more than 12mils (305 microns) thick can be susceptible toexternally applied stress. These thick coatingsmay experience flaking and disbonding, even

under very slight external stress. The coatingcan fracture at the interface between separatezinc-iron intermetallic layers. There will be a 0.1to 0.3 mil (2.5 - 8 microns) thick layer of zinc-iron intermetallic left on the bar, while the restof the zinc coating has flaked away.

The second factor affecting coating thick-ness is the blend of various bar sizes in a rein-forcing steel assembly. Each different size barwill develop a zinc coating at a different rate.

Larger bars must be kept in the zinc bath for alonger time in order to develop the minimumrequired thickness. In an assembly with differentsize bars, the smaller ones tend to have thicker-than-normal coatings because of the need tokeep the larger bars in the bath for the requiredtime.

COATING APPEARANCEASTM A 123 and A 767 (see page 20) require

that the zinc coating have no bare spots and befree of blisters, flux spots or inclusions, andlarge dross inclusions. The same specificationsalso state that a matte gray finish is not in and

of itself a cause for rejection. The matte grayfinish is a sign of accelerated growth of the zinc-iron intermetallics due to steel with high levelsof silicon. Cold-working may also result in thisappearance. The ability of a galvanized coatingto meet its primary objective of providing corro-sion prevention should be the chief criteria inevaluating its overall appearance and in deter-

mining its suitability.

The galvanized coating must be continuousto provide optimum corrosion prevention.Handling techniques for galvanizing require theuse of chain slings, wire racks or other holdingdevices to lower material into the zinc bath.Chains, wires and special fixtures used to handlepieces may leave a mark on the galvanized item.These marks are not necessarily detrimental to

the coating and are not a cause for rejection,unless they have exposed the bare steel or cre-ated a handling hazard for erection personnel. Ifnecessary, these areas can be adequatelyrepaired according to ASTM A 780 (see page 20).

The surface roughness of the reinforcingsteel after galvanizing also depends on theamount of silicon in the reinforcing steel. Oftena matte gray coating will have a rough surface.This does not affect the performance of the

reinforcing steel or the galvanized coating asthe rebar is embedded in concrete.

VISUAL INSPECTION GUIDEA visual inspection should be performed at

the galvanizers facility to ensure compliancewith the coating appearance requirements. Thefollowing are rare coating conditions that mayoccur.

Bare Spots - Gross uncoat-ed areas should be rejected.Small bare areas may berepaired according to ASTMA 780 (see page 20). Some ofthe causes of bare spots are:1. Incomplete surface cleaning: Remnantsof paint, oil, grease, scale or rust cause uncoat-ed areas. The molten zinc does not bond tosuch residues.

ASTM standardsrequire the zinc coat-

ing to be free ofmajor imperfecti ons.

4

FIGURE 9 - Sandelin Curve


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2. Welding slag: In assem-blies that have been welded,slag deposits from weldingprocedures are resistant tothe normal cleaning solu-tions used in the galvanizing

process and must be mechanically removed.

3. Overdrying: If the time between preflux-ing and galvanizing is too long, or the dryingtemperature is too high, the steel may rust dueto evaporation of the preflux, and the zinc willnot bond to these rusted areas.

4. Excessaluminum: If the aluminum con-centration in the zinc bath exceeds 0.01%, theremay be an occurrence of dark areas on the coat-ing surface.

5. Articles in contact: Thezinc in the galvanizing bathshould have free access to allparts of the surface. Articlesshould not be in contactthroughout the galvanizingprocess.

Dross Prot rusions - Drossis the zinc/iron alloy thatforms in the galvanizing ket-tle. Dross usually settles on

the bottom of the kettleand, if stirred up from thebottom, can attach to steelbeing galvanized. Commonly, the galvanizedcoating will form around the dross particles,although rough surfaces may result. This is notcause for rejection unless safe handling is com-promised or removal due to handling will leavea spot under the dross particle.

Blisters & Slivers - Blisters and slivers some-times form as a result of surface and/or subsur-face defects in the steel being galvanized. Thepossibility for this occurrence can be minimizedby communication among galvanizer, fabricator,and steel supplier throughout the projectsdesign phase.

Lumps & Runs - Areas of thicker coating,sometimes resulting from fast withdrawal ratesor lower zinc bath temperatures, are not detri-mental to coating performance.

Flux Inclusions - Zincammonium chloride, orflux, may adhere to

steel being galvanized.Flux inclusions are notcause for rejection,assuming the underlyingcoating is sound and theflux deposits are removed.

Ash Inclusions - Zinc ash isthe oxide film that developson the surface of the molten

zinc. Ash inclusions pickedup from the surface of thebath during withdrawal haveno detrimental affect on cor-

rosion prevention performance and are notcause for rejection.

Gray or Mottled CoatingAppearance - Exposed zinc-iron alloy layers, not coveredby a layer of free zinc, result

in a matte gray or mottledcoating. This may happenover the entire coating or inisolated areas. Steel chemistry contributes tothis occurrence. Because coating appearancedoes not affect the corrosion prevention provid-ed, matte gray or mottled coatings are notcause for rejection.

Brown Staining - Ifcoatings with exposedintermetallic layers(zinc-iron alloy layers)are exposed to the envi-ronment, brown stainingmay appear. This results

from the interaction between iron in the inter-metallic layer and the atmosphere. Coating per-formance is not affected.


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Rust Staining - If galva-nized coatings come intocontact with bare steel(chains used in transporta-tion, etc.), there may appearto be rust staining on thegalvanized steel surface. This

is actually a superficial occurrence; the staining

may be cleaned off before end-use.

Wet Storage Stain -The naturally occurringformation of a tena-cious, abrasion-resist-ant zinc carbonate pati-na provides yet anoth-er component to theprotection afforded by

galvanizing. The formation of this patinadepends on the galvanized steels beingexposed to freely circulating air.

Stacking galvanized articles closely togeth-er for extended periods of time, thereby limitingaccess to freely circulating air, can lead to theformation of a white powdery product common-ly called wet storage stain.

Wet storage staining is often superficial,

despite the possible presence of a bulky, whiteproduct. In the vast majority of cases, wet stor-age stain does not indicate serious degradationof the zinc coating, nor does it necessarily implyany likely reduction in the products expectedservice-life.

If wet storage stain does form, the objectsshould be arranged so that their surfaces dryrapidly. Once dry, most stains can be easilyremoved by brushing with a stiff bristle (notwire) brush. If the affected area will not be fullyexposed in service or if it will be subjected toan extremely humid environment, even superfi-cial white films should be removed with a stiffbristle brush.

GALVANIZED REINFORCING

STEEL TESTINGIn addition to visual inspection, different

properties and characteristics of hot-dip galva-nized rebar may also be tested. These tests mayneed to be performed on lots of steel to ensurethat they meet relevant standards, or on triallots before they are put into end-use. Accreditedlabs experienced with the individual test proce-dures should perform these tests.

Bond Strength Test - The bond of the hot-dipgalvanized reinforcing bar to the concrete canbe tested according to ASTM A 944 (see page20). The bond strength relies heavily on thedeformation of the bar and not as much on theactual bond between the zinc and the concrete.

For plain bars with no deformation, the bondbetween the zinc and the concrete becomesvery important. Pullout strength of hot-dip gal-vanized reinforcing steel has been tested manytimes, and the values of bond strength areequivalent to, or better than, black steel bondstrength, as illustrated in Table 3, page 10.

Chromate Finish Test - If chromate coating isrequired, the existence of chromates may beverified using the method described in ASTM B

201 (see page 20). Because chromate conversioncoatings will weather away fairly quickly, barschromated after they were galvanized mayexhibit no chromate by the time they areembedded in the concrete.

Embri t t lement Tests: Higher strength barsthat have had considerable cold working may besusceptible to embrittlement during the galva-nizing process. Guidelines for fabricating bars tobe hot-dip galvanized are provided in ASTM A143 and ASTM A767 (see page 20). Whenembrittlement is suspected, ASTM A 143 (seepage 20) designates the appropriate test methodto determine the presence of embrittlement.

Accelerated Aging Test : Efforts have beenmade in many zinc-coated steel applications todevelop the correct test method to determine aproper accelerated lifetime. The standard testfor corrosion prevention system is ASTM B 117

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(see page 20). ASTM Committee G-1 onCorrosion of Metals has jurisdiction over the saltspray standards B 117 and G 85 (see page 20).The Committee passed the following resolutionregarding the use of B 117:

ASTM Committee G-1 on the Corrosion ofMetals confirms that results of salt spray (fog)

tests, run according to ASTM standard designa-tion B 117, seldom correlate with performancein natural environments. Therefore, theCommittee recommends that the test not beused or referenced in other standards for thatpurpose, unless appropriate corroborating long-term atmospheric exposures have been conducted.

ASTM B 117 and B 368 (see page 20) arebest used as quality control tests assuring that

the day-to-day quality of products and manufac-turing processes are optimized. There are anumber of other corrosion tests which can beused for predicting performance in service.

Salt spray tests cannot be used to accurate-ly test zinc-coated steel because they acceleratethe wrong failure mechanism. Without a properwet/dry cycle, the zinc coating cannot form pati-na layers. The absence of a patina layer allowsconstant attack of the zinc metal and gives a

very low prediction of the zinc coating lifetime.Additionally, because the corrosion rate of zincembedded in concrete is significantly less thanthat of zinc in atmospheric conditions and hasnever been subject to long-term analysis, corre-lation to salt spray tests is impossible.

FIELD PERFORMANCEOF GALVANIZEDREINFORCEMENTVERTICAL CONSTRUCTION

The Eggat the Empire Center Plaza, a per-

forming arts center in Albany, N.Y., is a massiveundertaking of architecture, combining aesthet-ics and function, in a concrete and steel form.Because of its use of hot-dip galvanized rebar,this extravagant design will give citizens and vis-itors of Albany decades of enjoyment.

Despite its name and elegantly simpledesign, The Eggis a pillar of strength, literally.The Eggbalances on a concrete and steel stemextending six stories into the ground.

The shell of The Eggis shaped by a heavilyreinforced concrete girdle that helps keep itsshape and directs the weight of the structureonto the supporting pedestal and stem.

The housing

barracks at t heU.S. Coast

Guard Academywere built with

galvanized rein-forcing steel to

protect thebuilding andconcrete from

corrosion andspalling.

Extensive use of hot-dip galvanized reinforcement,including this surrounding wall, was specified for a

hospital in Australia. Galvanizing will help keep cor-rosion from creating severe spalling problems in this

structure, located in the coastal city of Katingal,home to a highly corrosive marine environment.


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Adding even more durability to this decep-tively fragile structure are miles of galvanizedrebar, weaving in and out of the shell and stem.

Construction of The Eggbegan in 1966 andtook 12 years to complete. Today, The Eggremains a beautiful piece of rust-free architec-ture.

HORIZONTALCONSTRUCTION

Both the Athens and Tioga Bridges arestrengthened and protected from corrosion byhot-dip galvanized reinforcing steel.

They both are heavily traveled routesbetween industrial areas of Pennsylvania and the

Five Finger Lakes area of New York. Afterexperiencing over 25 years of heavy snowfall,consequently exposing the bridge to corrosive,

chloride-containing road salts used to keep thebridges free from ice and snow accumulation,each bridge contains galvanized rebar that on anaverage measured 7.0+ mils (178 microns) ofzinc. Because the galvanized coating continuesto provide unsurpassed corrosion prevention tothe reinforcing steel, both bridges will continueto be maintenance-free for an additional 20 to30 years.

The Pennsylvania DOT makes extensive use of

galvanized rebar. The bridge deck of theSchuylkill River Expressway in Philadelphia is

protected by 400 short tons (368 Mtons) of gal-vanized rebar. After over a decade of service,

the rebar is in excellent condition.

For over 20 years galvanized rebar has provided

the Boca Chica Bridge near Key West, Fla., withmaint enance-f ree corrosion prevent ion.

Galvanized rebar has helped avoid traffic-snarling repairs of thi s 2,573-foot -long (784 m),

42-foot-wide (13 m) bridge. Despite heavy traf-fic and humid saltwater conditions, core sam-

ples show the galvanized rebar to have an aver-age coat ing thickness of 4 mi ls (102 m icrons)with no detectible signs of corrosion.8

Athens Bridge

Tioga Bridge


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ACI Committee 222. Corrosion of Metals in Concrete; American Concrete Insti tute, 222R-85, 1985.

Adnrade, C. et al. Corrosion Behavior of Galvanized Steel in Concrete; 2nd International Conference on Deteriorationand Repair of Reinforced Concrete in the Arabian Gulf; Proceedings Vol. 1, pp. 395-410, 1987.

Arup, H. The Mechanisms of the Protection of Steel by Concrete; Society of Chemical Industry Conference ofReinforcement in Concrete Construction; London, June 1983.

Structures - A Scientific Assessment; CSIRO Paper, Sydney, 1979.

Bird, C.E. Bond of Galvanized Steel Reinforcement in Concrete; Nature, Vol. 94, No. 4380, 1962.

Breseler B. & Cornet I. Galvanized Steel Reinforcement in Concrete; 7th Congress of the International Association ofBridge and Structural Engineers, Rio de Janeiro, 1964.

Chandler, K.A. & Bayliss, D.A. Corrosion Protection of Steel Structures; Elsevier Applied Science Publishers,pp. 338-339, 1985.

Cornet, I. & Breseler, B. Corrosion of Steel and Galvanized Steel in Concrete; Materials Protection, Vol. 5, No. 4,pp. 69-72, 1966.

Concrete Institute of Australia. The Use of Galvanized Reinforcement in Concrete; Current Practice Note 17,September 1984. ISBN 0 909375 21 6.

Duval, R. & Arliguie, G.; Memoirs Scientifiques Rev. Metallurg; LXXI, No. 11, 1974.

Galvanizers Association of Australia. Hot Dip Galvanizing Manual; 1985.

Hime, W. & Erlin, B. Some Chemical and Physical Aspects of Phenomena Associated with Chloride-Induced Corrosion;Corrosion, Concrete and Chlorides; Steel Corrosion in Concrete: Causes and Restraints; ACI SP-102, 1987.

Hosfoy, A.E. & Gukild, I. Bond Studies of Hot Dipped Galvanized Reinforcement in Concrete; ACI Journal, March,pp. 174-184, 1969.

India Lead Zinc Information Centre. Protection of Reinforcement in Concrete, An Update, Galvanizing and OtherMethods; New Delhi, 1995.

International Lead Zinc Research Organization. Galvanized Reinforcement for Concrete - II; USA, 1981.

Kinstler, J.K. Galvanized Reinforcing Steel - Research, Survey and Synthesis; International Bridge Conference Special

Interest Program, Pittsburgh, PA, 1995.

MacGregor, B.R. Galvanized Solution to Rebar Corrosion; Civil Engineering, UK, 1987.

Page, C.L. & Treadway, K.W.J. Aspects of the Electrochemistry of Steel in Concrete; Nature, V297, May 1982,pp. 109-115.

Portland Cement Association. An Analysis of Selected Trace Metals in Cement and Kiln Dust; PCA publication SP109,1992.

Roberts, A.W. Bond Characteristics of Concrete Reinforcing Tendons Coated with Zinc; ILZRO Project ZE-222, 1977.

Tonini, D.E. & Dean, S.W. Chloride Corrosion of Steel in Concrete; ASTM-STP 629, 1976.

Warner, R.F., Rangan, B.V., & Hall, A.S. Reinforced Concrete; Longman Cheshire, 3rd edition, pp. 163-169, 1989.

Worthington, J.C., Bonner, D.G. & Nowell, D.V. Influence of Cement Chemistry on Chloride Attack of Concrete; MaterialScience and Technology; pp. 305-313, 1988.

Yeomans, S.R. & Hadley, M.B. Galvanized Reinforcement - Current Practice and Developing Trends; AustralianCorrosionAssociation Conference, Adelaide, 17 pp., November, 1986.

Yeomans, S.R. Corrosion Behavior and Bond Strength of Galvanized Reinforcement and Epoxy Coated Reinforcement inConcrete; ILZRO Project ZE-341, June, 1990.

Yeomans, S.R. Comparative Studies of Galvanized and Epoxy Coated Steel Reinforcement in Concrete; Research ReportN0. R103, University College, Australian Defense Force Academy, The University of New South Wales, 1991.

Yeomans, S.R. Considerations of the Characteristics and Use of Coated Steel Reinforcement in Concrete; Building and

Fire Research Laboratory, National Institute of Standards and Technology, U.S. Department of Commerce, 1993.

ADDITIONAL RESOURCES


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AMERICAN SOCIETY FOR TESTING & MATERIALS (ASTM)A 90 Test Method for Weight (Mass) of Coating on Iron and Steel Articles

with Zinc or Zinc-Alloy Coatings

A 123 Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and SteelProducts

A 143 Safeguarding Against Embrittlement of Hot-Dip Galvanized StructuralSteel Products and Procedure for Detecting Embrittlement

A 615 Specification for Deformed and Plain Billet-Steel Bars for ConcreteReinforcement

A 616 Specification for Rail-Steel Deformed and Plain Bars for ConcreteReinforcement

A 617 Specification for Axle-Steel Deformed and Plain Bars for ConcreteReinforcement

A 653 Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-IronAlloy-Coated (Galvannealed) by the Hot-Dip Process

A 706 Specification for Low-Alloy Steel Deformed and Plain Bars for ConcreteReinforcement

A 767 Specification for Zinc-Coated (Galvanized) Steel Bars for ConcreteReinforcement

A 780 Practice for Repair of Damaged and Uncoated Areas of Hot-Dip

Galvanized CoatingsA 944 Test Methods for Comparing Bond Strength of Steel Reinforcing Bars

to Concrete Using Beam-End Specimens

B 117 Practice for Operating Salt Spray (Fog) Apparatus

B 201 Practice for Testing Chromate Coatings on Zinc and Cadmium Surfaces

B 368 Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing(CASS Test)

B 487 Test Method for Measurement of Metal and Oxide Coating Thicknessof Microscopial Examination of a Cross Section

B 602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings

E 376 Practice for Measuring Coating Thickness by Magnetic-Field of Eddy-Current (Electromagnetic) Test Methods

CANADIAN STANDARDS ASSOCIATION (CSA)G 164 Galvanizing of Irregularly Shaped Articles (Canadian specification)

SPECIFICATIONS

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American Galvanizers AssociationProtecting Steel for Generations6881 South Holly Circle, Suite 108Centennial, Colorado 80112Phone: 800-468-7732Fax: [email protected]

aga - a guide to specifying and inspecting hot-dipped galvanized steel

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