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??Des:gnation:D6386-99(Reapproved 2005)
???
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.
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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 [email protected],
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
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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
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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
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{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
"t y srd,
'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
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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
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*rcnr wtiw.
. . !hi? lydaq is qyrighted by asTM tntematic//,al, I oo Baft
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"r .1' :.JTftt.FllrrF inrf,r.Tl$}T'; r