1、Designation: D7396 14Standard Guide forPreparation of New, Continuous Zinc-Coated (Galvanized)Steel Surfaces for Painting1This standard is issued under the fixed designation D7396; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This guide covers surface cleaning and various methodsfor treating new, continuous zinc-coated (galvanized)
3、 steelsurfaces produced by either the hot-dip method or by electro-plating. This guide is applicable to only surface preparation forapplication of liquid paint and coating products, and not forpowder coating applications. This guide covers surfaces thathave not been treated previously at the mill to
4、 providetemporary protection against staining by moisture other than byeasily removed protective oils (see Appendix X1). For prepar-ing surfaces of new or weathered items of zinc-coated steelproduced by batch processing, refer to Practice D6386.1.2 The values stated in SI units are to be regarded as
5、 thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the
6、 applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A780 Practice for Repair of Damaged and Uncoated Areasof Hot-Dip Galvanized CoatingsD4285 Test Method for Indicating Oil or Water in Com-pressed AirD6386 Practice for Preparation of Zinc (Hot-Dip Galva-
7、nized) Coated Iron and Steel Product and HardwareSurfaces for PaintingD6492 Practice for Detection of Hexavalent Chromium OnZinc and Zinc/Aluminum Alloy Coated Steel2.2 SSPCThe Society for Protective Coatings Standards:3Surface Preparation Specification No. 1 Solvent CleaningSurface Preparation Spec
8、ification No. 2 Hand Tool CleaningSurface Preparation Specification No. 3 Power Tool Clean-ingSurface Preparation Specification No. 16 Brush-Off BlastCleaning of Coated and Uncoated Galvanized Steel,Stainless Steel, and Non-Ferrous MetalsPaint Specification No. 27 Basic Zinc Chromate-Vinyl Bu-tyral
9、Wash Primer3. Summary of Guide3.1 This guide describes surface cleaning and treatmentmethods that provide galvanized surfaces suitable for painting,specifically so that an applied coating system can develop theadhesion necessary for satisfactory service life.3.2 Eight methods of treatment (Note 1 an
10、d Note 2) arecovered as follows:3.2.1 Method AZinc Phosphate Treatment.3.2.2 Method BChromate Treatment.3.2.3 Method CAqueous Chromic-Organic Treatment.3.2.4 Method DAcid-Curing Resinous Treatment.3.2.5 Method EAnnealing Heat Treatments.3.2.6 Method FAmorphous Complex-Oxide Treatment.3.2.7 Method GA
11、brasive Blast Cleaning.3.2.8 Method HFluro-Titanic/Zirconic Polymer Treat-ment.NOTE 1Materials employed in these methods of treatment areavailable from a number of sources as proprietary compounds or methods.Selection may be made from available sources.NOTE 2The use of solvents containing volatile o
12、rganic compounds toprepare or treat the surface of metal components contributes to airpollution in the same manner as the use of solvent containing paints andcoatings. The user of this guide must determine the applicability ofappropriate regulations governing the volatile organic compound contentof
13、the materials used in a shop application (Miscellaneous Metal Parts),field painting (Architectural), or specific process industry.3.3 Variations in surface preparation produce end conditionsthat differ and hence do not necessarily yield identical resultswhen paints are subsequently applied. Service
14、conditions will1This guide is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.Current edition approved Dec. 1, 2014. Published January 2015. Originallyappro
15、ved in 2007. Last previous edition approved in 2008 as D7396 08. DOI:10.1520/D7396-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary
16、 page onthe ASTM website.3Available from Society for Protective Coatings (SSPC), 40 24th St., 6th Floor,Pittsburgh, PA 15222-4656, http:/www.sspc.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
17、PA 19428-2959. United States1dictate the type of surface preparation to be selected, althoughthe quality produced by any individual method may vary withdifferent zinc coatings.3.4 Galvanized surfaces are treated by using various meth-ods and apparatus; satisfactory application may be made at thefoll
18、owing locations:Mill Plant FieldMethod A Y Y YMethod B Y Y .Method C Y Y .Method D Y Y YMethod E Y . .Method F Y Y .Method G Y Y YMethod H Y Y .3.5 This guide does not describe the cleaning necessary toprovide a zinc-coated (galvanized) surface suitable for theapplication of the treatments. Many cle
19、aning methods areapplicable and the preferred method should be agreed uponbetween the purchaser and the supplier.NOTE 3Most producers of zinc-coated (galvanized) steel sheets andcoils have adopted the practice of applying an inhibitor to the zinc surfaceto give temporary protection against staining
20、by moisture during shippingor storage. Some of these inhibitors interfere with proper reaction of mostof the treatments described in these methods, and an unsatisfactory surfacefor painting results. It is strongly recommended that the purchaser consultthe supplier of the chemical treatment to be use
21、d as to the suitability of thezinc surfaces for treatment by any of these methods.3.6 Surface CleaningGalvanized surfaces must be cleanand free of soluble salts, oil and grease before they are treated.Adhesion problems have been experienced with newly galva-nized articles that have been water quench
22、ed or treated withchromate conversion coatings. These two post-galvanizingprocesses, water quenching and chromate conversion coating,are not recommended for galvanized articles that are to betreated before painting. The presence of chromate conversioncoatings on the surface of the galvanized steel c
23、an be detectedusing Practice D6492.3.6.1 Aqueous Alkaline CleaningAn alkaline solution, pHin the range of 11 to 12 definitely not greater than 13, can beused to remove traces of oil, grease, or dirt.An alkaline cleaneris unsuitable for removal of heavy build-up of zinc oxide orwet storage stain. See
24、 the American Galvanizers Publication,Wet Storage Stain,4for description of these conditions. Thealkaline solution is nominally 2 to 5 % sodium compounds,with small additions of emulsifying, chelating, or sequesteringagents, or combinations thereof. This solution can be appliedthrough immersion in a
25、 tank filled with the solution, byspraying, or by brushing with a soft bristle brush, usually nylonand not steel or copper. When dipping or spraying, the solutionworks best in the temperature range from 60 to 85C (140 to185F). After cleaning, rinse thoroughly in hot water or waterunder pressure. All
26、ow to dry completely before proceeding.Whenever galvanized steel is rinsed, heated drying to acceler-ate the complete removal of water from the surface is desirable.3.6.2 Solvent CleaningTypical cleaning solvents, such asmineral spirits or high-flash naphtha, can be used to remove oiland grease. The
27、 procedure to be used is as specified in SSPCSurface Preparation Specification 1. Proper rags or brushesshould be used to wipe the galvanized parts. (WarningTheserags or brushes should be cleaned or recycled often, since oilcan accumulate on their surfaces and be transferred back to thegalvanized pa
28、rt. Small parts may be dipped or cleaned inultrasonic baths of solvents.) After cleaning, rinse thoroughlyin hot water or water under pressure. Allow to dry completelybefore proceeding. Whenever galvanized steel is rinsed, heateddrying to accelerate the complete removal of water from thesurface is d
29、esirable.3.6.3 Hand or Power Tool CleaningHand or power toolcleaning may be used to clean light deposits of zinc reactionby-products, such as wet storage stain or salts, as specified inSSPC Surface Preparation Specification 2 or 3.4. Significance and Use4.1 This guide describes procedures that can b
30、e used toprepare new zinc-coated surfaces for painting and improve thebond of paint to the zinc surface.5. Processes5.1 Method A, Zinc Phosphate TreatmentThis conversion-coating method consists of reacting the zinc surface in a zincacid phosphate solution containing oxidizing agents and othersalts f
31、or accelerating the coating action. The zinc surface isconverted to a crystalline phosphate coating of the propertexture to inhibit corrosion and increase the adherence anddurability of the paint film. Such treatments are recommendedfor product finishes and may be carried out by immersion,spray, or
32、brush application.5.2 Method B, Chromate TreatmentThis treatment con-sists of a dip or spray with a dilute solution of a mixture ofchromium trioxide and other acids, with the proper accelerator,for a period from 5 to 30 s at room temperature to 55C(130F) to provide a thin amorphous chromate coating
33、thatincreases corrosion resistance and paint adhesion.5.3 Method C, Aqueous Chromic-Organic TreatmentsCertain water-soluble resins, when properly formulated withchromium compounds, may be applied to zinc surfaces byroller coat or other suitable means, such as dip and squeegeerolls. This may be done
34、over a wide temperature rangeprovided the film is properly baked or cured, or both, asrequired by the paint system to be applied. The resultantcoating provides a corrosion-resistant film that increases theadhesion of applied paint films.5.4 Method D, Acid-Curing Resinous Treatment (Vinyl WashPrimer)
35、 (See SSPC-Paint No. 27)This surface treatment isbased on the application of an acid-curing resinous film ofapproximately 8 to 13-m (0.3 to 0.5-mil) thickness. Thetreatment is based on three primary components: a hydroxyl-containing resin, a pigment capable of reacting with the resinand an acid, and
36、 an acid capable of insolubilizing the resin byreacting with the resin, the pigment, and the zinc surface. Thefilm is usually applied by spray, but may be applied by brush,dip, or roller coater. Under normal conditions it will drysufficiently for recoating within 30 min, and within8hitwillnot be sof
37、tened by organic solvents commonly used in paint4Wet Storage Stain (1997), available from American Galvanizers Association,6881 South Holly Circle, Suite 108 Centennial, Colorado 80112,http:www.galvanizeit.org.D7396 142coatings. The film has good adhesion to the metal substrate andpromotes good adhe
38、sion of most subsequent organic coatingsto itself. Two types of this treatment are available: (1)two-package material to be used the day it is mixed and (2)one-package material that has package stability and does notrequire daily preparation.NOTE 4It may be difficult to control the dry film thicknes
39、s within theparameters of this specification when applied by brush, roller, or dipcoater.5.5 Method E, Annealing Heat TreatmentsUnder the con-trolled conditions obtainable in a mill, hot-dip galvanizedsurfaces may be converted and alloyed with the base metal tochange the surface character of the zin
40、c coating and make itmore receptive to paint. This surface can be further improvedby treating in accordance with Methods A, B, C, or D.5.6 Method F, Amorphous Complex-Oxide TreatmentThissurface treatment method consists of reacting the zinc surfacein an alkaline solution containing heavy metal ions
41、for a periodof 5 to 30 s at 45 to 70C (115 to 160F). The surface of thezinc is converted to a nonmetallic, amorphous, complex-oxidecoating that inhibits corrosion and increases the adhesion anddurability of paint finishes. The treatment can be carried out byimmersion or spray application.5.7 Method
42、G, Abrasive Blast TreatmentAbrasive sweepor brush blasting in accordance with procedures described inSSPC SP 16 for the surface preparation methods only uses arapid nozzle movement roughening the galvanized surfaceprofile. The abrasive material must be chosen carefully toprovide a stripping action t
43、hat removes the oxide reactionproducts without excessive removal of the zinc. One of thematerials successfully used is aluminum/magnesium silicate.Particle size should be in the range of 200 to 500 micrometers(8 to 20 mils). Other materials that can be used are soft mineralsands with a Mohs hardness
44、 of 5 or less, organic media such ascorncobs or walnut shells, corundum, and limestone. Forreactive steel with all-alloy coatings which may have compro-mised adhesion, even the relatively low-pressure blast of 0.15to 0.25 MPa (20 to 40 psi) can be too great, causing adhesionproblems. Care must be ta
45、ken to leave zinc layers intact. Oilcontamination of the compressed air will degrade adhesion tosweep-blasted hot-dip galvanized surfaces (Test MethodD4285). Care is needed in averting this type of contamination.The purpose of sweep blasting is to deform, not remove thegalvanized metal. Any area fal
46、ling below the required zincthickness, before or after sweep blasting, shall be repaired inaccordance with Practice A780. Sweep blasting of zinc shall benot less than 110 m2/h (1200 ft2/h) using these abrasivematerials. The substrate shall be maintained at a temperature ofat least 3C (5F) above the
47、dew point temperature.5.8 Method H, Fluro-Titanic/Zirconic Polymer TreatmentThis treatment method is a chromium free analog of thesolutions commonly employed under Method C. It consists ofa combination of poly(acrylic acid) with copolymer resins and0.01 to 0.1 M H2TiF6or H2ZrF6. The solution can be
48、appliedto the galvanized steel surface by spray, dip, squeegee or rollercoating. The excess solution is spun-off or otherwise removedfrom the metal surface, resulting in a dry in-place surfacetreatment. The finished surface consists of a complex oxidepolymer matrix bound to the zinc metal.5.9 Coatin
49、g Application Time FrameBlow down preparedsurface with clean, compressed air following surface prepara-tion. In some atmospheric conditions, such as high humidity orhigh temperature or both, the formation of zinc oxide on thefreshly prepared surfaces will begin very quickly. Zinc oxideformation is not visible to the unaided eye; therefore, in anyatmosphere, painting should be started within an hour aftersurface preparation.6. Keywords6.1 acid-curing resinous treatment; amorphous complex-oxide treatment; annealing heat treatment; chromate; chroma
