??Des:gnation:D6386-99(Reapproved 2005)

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Standard Practice for

~1, Scope

i t Thls practicc dcscribes illcthodb or prcpdiing surtaces ornew and weadlered hotdip galvanized steel for pnting.

Hotdp galvanlzed steel is produced by the ttersion ofibcated or unfabcated products h a bath of inolten zinc.aspecined m speciflcations A 123 or A 153/A153M.This

_practtce covers sttace preparaton on iron and steel productsd hardware dlat have not been painted prevbusly.Galvaized sttes may have bcen treated with protective coatingsLO preVent thecurrence of wet storage staln.This practice

does not apply to shect galvanized steel productsortO the coil)adng or conunuous roner coating processes.1.2 The values stated ln SI units are to be regarded as dle

_standardo The values given in parentheses are For infoll..atiOn^ly.

1.32s`

s

0"ss ``o C`S, ,SS`' ` ` .fr J`sP: o/``S`sttb, sara c`s r`f ttica

gJara,irar"S`

-2.Referenced Documents2.l AStty srarldar2A123 Specincat10n for Zinc oIOtDip Galvanized)COat_

_ ings on lron and Steel ProductsA153/A1531 Speciflcatlon for Zinc Coatlng(HOtDip)onlron and Steel HardwareA780 Pracice for Repnlr of I)amaged and Uncoated Areas~ of HotDip Calvanlzed CoatmgsB201 Pracdce for Tesdng Chromate Coatngs on Zinc andCaum Sraces

_ E376 Practice for Measung Coating Thickness byMagneticField or EddyCurrent C31eCtrOmagnetic)TeStMethods

rThis practice is under the jurisdiction of ASTM Corilnitte DOl on Paint andI

-iated Coatings, Materials, and Applications, and is the direct rcsponsibility ofSubcomminee DOl.tt5 on Indusrial Protctive Coatings.

-

Currcnt edition approved July I 2fi)5. Published August 2005. Originally: rroved in 1999. Last previous edition approved in 1999 as D6386-99.

2 For rcfercnced ASTM standards, visit the ASTM website, wwv.astm.org, orcontact ASTM Customer Service at service@astm.org, For Annwl Book of ASTM

-Standords volume information, rcfer to the standard's Document Summary page on

t ASTM website.

2 2 5`rPCrJ`Cgs 5`lC

j

"

Sulcc Prcptttr.ltin SrCtincatlon Nc i Sol.ent Cicanin3

Sudace PrepFation Specilication No 2 Hand Tool Cleanlng

Surface Preparation Specincatlon No 3 Power Tool Cleanmg

Surface Preparation Speciflcation No.7 BrushDfF BlastCleaning

Paint Speccatlon No. 27 Bast Zinc ChromateVinylButyral Wash Primer

3. Summary of Practice3.l This practice describes the preparation methods that

provide clean and suitable galvanized surfaces for p^lnting,speciflcauy sO that an applied coadng systern can develop aleadhesion nccessa/for a satlsfactory service Lre.3.2 The zinc coating is constandy in a state of change.From

dle time the steel part is removed iom the galvanizing ketac,the exposed zinc coattng interacts widl the envlronment tofollll, arst ttc oxides, next ttnc hydroxides, and then zinccttbonates.4 The process of complete conversion of the outerlayer of zlnc carbonates can take up to two yearS of exposureto dle envronment, depeng on the lal climatologlcalcondidons.Durlng the nrst stage,known as newly galvanlzedsteel,dle exposed srace cOnsists mainly of znc metal with asmall anlount of zinc oxide.Dunnge second stage,known aspartiany weathered gvan17ed StCel, the exPoSed sJaceconsists nlalnly of zlnc odes and zhydrodes with some carbonates.At dle flnal stage, known as weatheredgalvanlzed steel, the exposed srace consists mainly ofwaterinsolublenc carbonatcs,some zllllc odeS,and rarely,zinc hydroxldes. le surface preparation for each of thesestages must be treated separately.3.3 Variations in sCace preparation produce end conditions

dlat difet hence they do not necessarily yield identical resultswhen paints are subsequendy apphed.Service conditions windictate the type of srace preparation to be selected,although

t Available ftom Society for Protective Coatings (SSPC), 40 24th St., 6th Floor,Piftsburgh, PA L52224656.

'This interaction is dcscribed in "Duplex Systems," van Eijnsbcrgcn, J.F.H.,Elsevier Science, New York, IYY 1994, nd n Zinc Hatdbook, Portec F., MarcelDekker. Inc., New Yodq NY 1991.

Preparation of Tinc (Hot-Dip Galvanized) Coated lron andStedl Product and HardwarC Surfaces for PaintinglThis standard is issued under the axed dcsignation D 6386: dle numttr inlmediately following the dcsignation indicates thc year oOn3mal adoption or,ln the cttc of resion,thc ycar of lt rcsion A numbcr in ParCntteses indicates me year Of ltapprovai Asupcrscpt epsilon teindicatcs all cditodai changc shcc ttc iast rcisionr rcapprol

Copynght o ASTM Intemational,100 3arr Harbor D"vo,PO Box C700,WOst Conshohockon,PA 194282959,Unlted Stas

dff o s:l86 - ee (2oos)the quality produced by any indidual process may vary withdirerent cOmpositiollls of the zinc srace.

4.Signincance and Use4.l This practice descHbes the procedures that can be used

to prepare new and weathered zinccoated surfaces on afterfabrication stcel products for painting,and that can improve thebond of pttnt to the zinc surface.

5 Processes for Newly Galvanized Steel51 N`G,

`S`The category of newly galva

nized steel reters to zinccoated steel that has no suracctreatinent after galvanizing such asvater quenching or chrolatc cnrsin toti[illg 11 .ls bccll givtinlzcd iithiil thcprevious 48 h There also should be no visible signs of zincoxlde or zlnc hydroxlde, which irst appear as a line uhiteoowder5.2S`'

r/2:4gHotdip galvanized suttaces generally are relattvely smooth after gvanizing.There may besome dick edges due to excess liquid zinc runofF dng thegalvaluzlng,or hgh spots h ale coatmg due to includedironzhc htemetallics(drosS)Or zinc oxide particles.hsehgh sPots and rough edges,such as the metal line,mustbe smoothed to avoid palnt alm gapS in dle areas of the highspots.5.2.l Zinc high spots,thosc that would cause pamtflhn gaps

such as dle rnetalp line,should be removed by clegvithhand or power tools as descHbed in SSPC Stlrfacc PreparationSpecincatiOn 2 o3 1he zinc should be removed until it islevel with the surrounding ttea, tndng care that tte basecoatlng is not removed by the cleaning IIlethods.After cleaning, thc srace shau be mspected for confo.1..ance to therequlred zinc ckness in accordance with SpeclflcauonsA123 or A 153/A153M umizmg a nlagnedc thckness insLument h accordancc widl Pracdce E 376.Any item fallingbelow tte required zinc dlickness,before or after removal ofany high spots, shau be repttd in accordance widl PracticeA780.5.35 `Clea

gHOtdip galvanized surfaces must beclean and tree or oil alld grease before they are palnted.Adhesion problems have been expenenced with newly galvadzed attcles that haveen water quenched or treated wiLlcomate conversion coatings. These o postgalvzingtreaments are not reconlmended for galvanized articles that arcto be panted.5.3.l A`Os AJ: CJ:agAn alkaline solution,pH

in the range of H to 12 dennitely not greater than 13,can beused to remove traces of oil,grease,or dirt.An alkaline cleaneris unsuitable for rernoval of heavy buildup of zlnc oxide orwet storage stain(sce Amecan Galvanizers Publications,Warsrarag`SraFP15,for descpdon of alese cOndidons),S5.4 forrelnoval of zinc oxide layen Thalkaline solutton nolrunany is2 to 5%sodiunl compounds,widl small addios of emulsifying,chelatmg,or sequesteng agents,or a combinationthereof This solution can be apphed through illlmersion in a

5 Avaable from Amencan Calvanlzers Assiadon,12200 E IliEAve.,No 204,Aurora.C080015376

tank aned with the solution,sprayod,or brushed with a sofbrisde brush, usuauy ny10n and not stecl or coppe Wheldipplng or spraylng,the soludon woFkS beStin the temperatunrttrm60 to 85C._Ater cleaning,nIIse thoroughly m howater or water under pressuFe.Allow to dry completely befonprocecdingo Whenever galvanized steel is rinsed,it is desrabllto usc heated drying to accelerate the complete removal owatr from the surface.5.3.2 Sb

`CI`

g Typlca cleaning solvents,such a

mineral sputs or highllash naphtha,can be used to remove oiand grease The procedure to be used is as specified in SSP(Surfacc Preparation Specincation l Proper rags or brusheshould be used tovipe the galvanized parts

N(: 1-Caution:These rags or brushes should be cleaned or recycleoften shce oil can accumulate on thetr suaces and be transtrred backdle galvzed palt. Smaparts may be dlpped or cleaned h ultrasonibaths of 3olvents Atter cleanlng,dnse thproughly in hot water or wateunder pressure Auow to dtt cOmpletely before preedlng

5.3.3 Har P`r b

:gHand or power toc

cleng inay be used to clean light deposits of zinc reactton blproducts, suCh as wetstorage stain, as specined in sSP(sracc Preparation SpincatiOn 2 or 3.5.4S2`Prapara

4-Hotdip galvanized sdaces haa layer of zinc oxide and zinc hydroxide that must be remove(before paint will adhere to the zinc coamlgo zinc coanggenerally are relatively smth and may be shghdy roughenelpor to palnmg.The fouowmg fOur methods may be used uprepare the galvanlzed surface for painmg.5.4.l Sw``31a:gAbrasive sweep or brush bltstlng

wich uses a rapid nozzle movement will roughen the galvanized surface pronle. The abrasive mateal must be choseiwith care to provide a smpping action without removing exceszinc layers.One of the mateals that has becn used successfully is alumnumagnesiunl silicate_Particle size should b`in the range of 200 to 500 (8 to 20s).Other matealthat can be used are soft nlmeral sands with a MOH hardnesof ttve or less,organic lneda such as conl cobs or wahsheus,cOrundum,and lllnestone. Depending on the value ohardness for the abrasive medium,blthg pressure may neelto be detemlmcd for the appropate nozzle to workpiec.distance, geomett of the component, and blting mediumFor some ananOy COatings,even the relatively lowpressurtblast of O.15 to O.25 NIPa(20 topsi)can be tgrealcausing cohesion probler.0contamination of the compresscd air win degrade p,lnt adhesion to sweepblastelhotdip galvanized surfaces. Care is nceded in averting ali Of COntamination.Care rnust be taken to leave zlnc layerhtact.The purpose of sweep blasting is to defom,not removthe galvamzed lnetal.Any area faing below ale requred zin(thickness,before or after sweep blasting,should be repaired ilaccordance with Practice A 780.TE procedure for this procescan be found in SSPC Surfacc Preparatn Specincation 7Sweep blasting of zinc should be not less dlan l10 m2/h(120ft2/h)uSing alesc abrase materials.e substrate should blmaintained at a temPcrame greatcr than 3C(5D aboVC th`dew point temperature.Fouowing abrasive blast cleaningsurfaces should be blown down with clean,compressed att llsome atinospheric conditions,such as high hunudit Or higI

36

4ffi o el46 - ee (2oos)temperature, or both, the formation of zinc oxide on the blastedsurface will besn very quickly, so the paint coating should beapplied immediately, within 60 min, after sweep blasting. Zincoxide formation is not visible to the naked eye: therefore. inany atmospherc, painting should be stated as soon ., po*ribl"after surface prcparation.

5.4.2 Zinc-Phosphate Treatment-This convenion-soetingprocess consists of rcacting the newly galvanized zinc surfaciin an acidic zinc phosphate solution ssntaining sxidiziagagents and other salts for accelerating the coating action. Thezinc surface is converted to a crystalline phosphate coating ofthe proper texture to inhibit corrosion and increase the adher-ence and durability of the paint film. This process may beapplied by immersion, spray or soft bristle brush application.After a time period of 3 to 6 min, the surface should be washedwith clean water and allowed to completely dry before appli_cation of the paint system. painting should take place ioonafter treabnent to avoid pick up of surface contaminants.

5.4.3 Wgsh Primer Treannent-T\is process involves theuse of a metal conditioner to neutalize surface oxides andhydroxides along with etching the surface. One example of awash primer is SSPC Paint Specification 27. The process isbased on three prinary components: a hydroxyl+ontainingresin: a pigment capable of reacting with re.sin and acid: an{an acid capable sf malcing the resin insoluble by reacting withthe rcsin, the pigment, and the zinc surface. The result is a filmrf approximately 8 to 13 pm (0.3 to e.J mits). Failures canrcur if the film exceeds 13 pm (0.5 nils). The film usually isapplied by spray but may be applied by soft bristle bmsh, diF,rr loller coater. Using these lattcr coating methods, it may be':fFcult to control fts fitm thickness. For drying tine prior to

copcoating, follow the manufacoret's instnrctions. This washprimer treatment may be better suited !o certain types of paintiystems. See SSPC Paint SpecificationZl for the best match ofhis treaEnent to a paint system.

5.4.4 Acrylic Passivation/Pretrcatment-T\e passivation/rtrament process consists of applying an acidic acrylicolution to the newly galvanized surface and then allowing it todry, forming 4 thin film coating. When applied, the solutionfirst reacts with the zinc surface forming a passivating conver-iion coating while simultaneously forming an acrylic coatingruitable for painting on top of the passivation layer. Theundedying conversion coating provides strong adhesion to the;alvanized surface while the thin fifm acrylic layer providesrarrier protection, which inhibits corrosion and provides alighly compatible surface for the application of organic paintfilms. There are versions of these solutions that cont in chromend versions without chrome. The application methods forhese water based heatuents arc dipping, flow coating, spray_

ing, or other approfriate means. Following application thercating is dried in an oven or in air. In some instances, the:oating is applied to hot-galvanized articles, in which case

separale drying is not necessary. Rinsing is not required. Thecoating is approximarcly l-pm (0.0+mils) thick. painting isrossible any time during a period of four months afterpplication, as long as the surface is free of visible zinc oxides

or zinc hydroxides; however, if harmful gsaraminants, such as'lust, dirt, oils, grease or deposits are present, they must be

removed with a 6ild atkatine degreasing solution (pH ll.5max) followed by a thorough rinse with hot watei 160"Cryglg temperature) tr a pressrlle wash, then thoroughlydried. This tmatueat is ap'plied in the ge!.,,anigrng plant or l-atjrin the paint shop. When applied in the paint shop, the surfacemust first be appropriately cleaned as just described to rcmovecontaminants picked up after galvaniz.ing.

5.4.5 Notifrcation of Surface Treatment-T\e paint shopmust be notified as to how the galvanized articles have beenprocessed and which surface treatment method, if any, is usedto prepare the surface.

6. Processes for Partially Weathercd Galvanized Steel6. 1 Before preparing the surface of partially weathered

galvanized steel, the surface must be checked for the presenceof chromate conversion coating. The presence of a chromateconversion coating can severcly impair the adhesion of somepaint coating sysoem. Chromate conversion coatings can beapplied at the galvanizing facility to protect the newly galva-nized surface from excessive growth of zinc oxide and zinchy&oxide, commonly called wet storage siain. The presence ofchromate conversion coatings can be detccted by the procedureoutlined in Appendix Xl. The removal of the cbromateconversion coating also is outlines in Appendix Xl. Thesurface preparation method described in 5.4.4 could testpositive for the prcsence of chrome. The surface p'rcparationtechnique described n 5.4.4 should not be removed if it testspositive for the presence of cbrome. This process is not achromate conversion coaring. If the galvanized surface hasthick edges or high spots, these should be removd see 5.2.1.when the high spots have been treated and the chromarc hasbeen removed completely by sanding tx swoep blasting inaccordance with 5.4.1, surfaces should be blowa down withclean, comlncsscd air. In some amospheric conditions, such ashigb humidity ot high tempraturc, or both, the formation ofzinc oxide on the blasted surface will begn very quickly so thepaint coating should be applied within 30 min after sweepblasting. Zinc oxide formation is not visible to the naked eye;therefore, in any atmospherc, painting should be as soon aspossible after surface preparation.

6.2 Beforc preparing the surface of partially weatheredgalvanized steel, the surface must be checked for the presenceof wet storage stein. Wet storage stein is the whitish zinccorrosion product forned when galvanized parts arc exposed tomoist air without sufrcient air circulation between the partsand is described in the American Galvanizen Associationhrblication, Wet Storage Srain. Wet storage srein consistsprinarily of beta zinc hydroxide and small percentages of zincoxide and zinc carbonate. Since wet storage 5tein is hygo-scopic and has a larger volume than zinc metal, paint adhesioncan be afiected seriously when painting over wet storage srrin.Careful bmshing with a mild zs6snia solution using a softbristle brush will rcmove mild cases of wet storage srrin.Thorough water rinsing must immediately follow the bnrshing.Morc severe cases of wet storage stain that have thick whirccorrosiou products ou the zinc surface, or even black corrosionproducts, can be cleaned using vigorous soft bristle brushingwith a mild acidic solution with a pH of 3.5 to 4.5, such asacetic acid or citric aci4 but not hydrochloric or sulfuric acid

37

{ff o dn6 - ee (2oos)solutions. Thorough waterrinsing must immediately follow thebru$ing. After the part has completely dried, the surfaceprofile should be applied in accordance with 5.4, and, then thesurfaces shouiri be biown down wrth clean, comp,ressed air. Ifno protective treatnent" such as those describe d n 5.4.2_5.4.4is applied, in some atnospheric conditions, such as highhumidity, or high temperature, or both, the formation of zincoxide on the surface will begin very quickly so the paintcoating should be applied within 30 min. if

" prot".tiu"

treaEnent is applied, it is not necessary to paint immediately.Zinc oxide formation is not visible to the nated eye; therefori,in any atmosphere, painting should be as soon as possible aftersurface preparation.

6.3 If there is no indication of either chromate conversion:ouqF or wet storage strin, the surface can be prepared asdetailed in Section 5.7. Processes for lVeathered Galvanized Steel

7.1 Fully weathered galvanizsd steel, as described rn 3.2,has developed a stable and finely etched surface that is vervsuited for paint coating adhesion. If there are organic contami_nants, such as oil, grease, or soot on the surface of the part,

XI.z [f zinc-coated steel to be painted is galvanized toorder, the order should prohibit the use of hexavalent cbro-mium humid-storage strain treatuents.

surface cleaning in accordance with 5.3 should be performecbefore any other cleaning is done.

7.2 The natrrra! corrosion of the zinc netal pioduccs ;roughened surface film consisting primarily of basic zinccarbonate. The surface preparation that is needed is a powelwash with warm water to remove loose particles from thesurface. The power wash should use water j;$ with a pressureof less than l0 Mpa (1450 psi) so a, not to damage theprotective film. This film is nanrrally roughened in its growthprocess, so no extra surface profiling is needed. Allow thesurface to completely dry before application of the paintsystem.

7.3 Fully-weathered galvamzed steel can be painted suc_9es;t1ftf with the application of appropriate paint systemsincluding primers and top coat paints. The use of pietrearments, such as those described in 5.4, can enhanie paintadhesion and extend long term performance.

E. Keywords8.1 galvanized steel; galvanizing; hot-dipped galvanizing.

painting; paint preparation; surfacing pr"paritiou zinc coatin!

APPENDU

(Nonmnndatory Information)xl' IDEMIT"nNG TIIE PRESENCE OFAI\D REMOVING CEROMATE TREATMENTS USEDAS WET STORAGE (ALSOCALLED IIT'MID.STORAGE) STAIN IIYHIBITORSXl'l oneof theinhibitorsusedbyproducersof zinc-coated x1.3.1 weathering the surfaces for six months, orstel is a hexavalent chromium solution. This treatment pre- xI.3.2 Abrading ile surfaces by sanding, orvents adhesion of many paint coatings to zinc coated steel x1.3.3 Sweep b'iast clean in accordance with 5.4.1.surfaces.

X1.4 The presence of hexavalent chromium on galvanizedsurfaces can be determined by spot tesring used practice B 20 l.

Xl.5 Conduct the spot test on several representative spotson each individual piece of galvanized steel.

Xl'3 Hexavalent chromium treatment can be removed from Xl.6 Test, in accordance with practice B 201, every piecegalvanized surfaces by one of the following three methods: of galvanized steel that is to be teated for painting.ASTM lntamatbnal bkg tro ,prgt'drlt tf4rr,dng tha vattdty of any patent rtghg aslxlfted in @nnrr;ton with any ltem mdntionedln this shnclard' use6 ol this stadad.arc ixprasay aaua-na aitdrmnaaoi ot w ralay a

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'nltent tigttF., an(t 0B riskof brtringcnwtt d str/t dglfr, an ennyh6no6 rrgraa&nttq. '

This siandadissttir,tb revis*n atanydne bytt.F r6qr,nsiuefrd',//,k*il @'7'nittfF aN mulf be reviawdewryfueyeaB etfrit not Evised, either rnwrovd or withdnwr' Your Cr,nmet# arc invited eihar tor reviskm ol this staded ot for a&itional stattr,aftlsaN slpuld b a&lressd to Asru htemattona! Heia,&uarten Your rrlmments witt r*llive caraful @nsihntion at a neeting ot thetas@nslae tadvftal amnittee, wlt*lt rou maf anea. tyou ta natyou@mton9 ii *t iani it,iriiri,rg-y* ",-rbmako yo,r,eyrsro.ow,to theAsfU Connitt*' on Sl',.da*, athez&rcss *rcnr wtiw.

. . !hi? lydaq is qyrighted by asTM tntematic//,al, I oo Baft Hatuot Ddve, po Bo( c7N, west hnstphe*en, pA t g428-2g5g,united states' hdffiial r$,r, (W q yultple qies) of iltis stan.#li may a a"na by urffihg ASTM at the atuvee&ress or at 6lo-(,2-9sas 6none1, a1/.&8fiz-es*; t6rl, n servi(F/lastm.oq (e4nait); or hrough the ASru website(w*w.estn.or0.

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