1、Designation: D1731 09 (Reapproved 2014)Standard Practices forPreparation of Hot-Dip Aluminum Surfaces for Painting1This standard is issued under the fixed designation D1731; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、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. Scope1.1 These practices describe procedures for the preparationof hot-dip aluminum surfaces for painting.1.2 This standard
3、may involve hazardous materials,operations, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability o
4、f regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D609 Practice for Preparation of Cold-Rolled Steel Panelsfor Testing Paint, Varnish, Conversion Coatings, andRelated Coating Products2.2 Military Standards:3MIL-DTL-5541 Chemical Conversion Coatings on Alumi-num and Alu
5、minum AlloysMIL-C-15328 Specification for Acid Wash PrimersMIL-M-10578B Metal Conditioner and Rust Remover(Phosphoric Acid Type)3. Types of Surface Preparations3.1 Two types of surface preparations are covered as fol-lows:3.1.1 Solvent Cleaning, and3.1.2 Chemical Treatments.3.2 These two types cover
6、 several methods as described inSection 5. Variations in surface treatment produce end condi-tions which differ and which do not necessarily yield identicalresults when paints are applied. Service conditions will dictatethe type of surface preparation that should be selected.4. Solvent Cleaning4.1 T
7、he surfaces may be prepared for painting by any of themethods for solvent cleaning described in 4.2 and 4.3.4.2 Method 1Manual swabbing or dip washing with asolvent such as mineral spirits or high flask solvent naphtha. Itis extremely difficult to produce a clean metal surface by thismethod. Accumul
8、ated contaminants in the solvent or on theswab are frequently redeposited on the surface being prepared.4.3 Method 2Solvent spray cleaning in accordance withMethod A, Procedure 1 of Practice D609.4.4 Method 3Vapor degreasing in special equipment inaccordance with the latest revision of Method A, Pro
9、cedure 2of Practice D609, employing trichlorethylene or perchloreth-ylene vapor. Solvent cleaning does not disturb the natural oxidefilm on the metal and may prove adequate for some applica-tions.5. Chemical Treatment5.1 The surfaces may be prepared for painting by any of themethods for chemical tre
10、atment (Note 1) described in 5.2 to5.9:NOTE 1Materials and procedures employed in these methods oftreatment are available from a number of sources as proprietary com-pounds or methods. Selection may be made from available sources. Thehexavalent chromium methods given are not recommended as hexavalen
11、tchromium is a known carcinogen.5.2 Method 1, Alkaline CleanersEtching alkalinesolutions, such as caustic soda, should be avoided because ofthe possibility of dissolving away the aluminum coatingthereby exposing the base metal. Since inhibited alkalinecleaners do not etch the surface, they can be us
12、ed to removegrease, oil, and other organic solids from hot dip aluminum.After alkali cleaning, the surface should be thoroughly rinsedwith clean water. Most often alkaline-cleaned surfaces aresubsequently processed by one of the following methods,described in 5.3 5.9.5.3 Method 2, Alcoholic Phosphor
13、ic Acid Cleaners Thistreatment involves the use of an aqueous solution of phos-phoric acid with alcohol or other organic solvents, togetherwith wetting agents, emulsifying agents, etc. The solution maybe applied by swabbing or dipping (preferably at a temperatureof 70 to 90F (21 to 32C). The solutio
14、n should remain on the1These practices are under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.07 onConversion Coatings.Current edition approved Nov. 1, 2014. Published November 2014. Originallyapproved in 1960. Last prev
15、ious edition approved in 2009 as D1731 09. DOI:10.1520/D1731-09R14.2For 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 page onthe ASTM we
16、bsite.3Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1surface for several minutes, followed by thorough rins
17、ing withclean water. A very thin phosphate film is formed which tendsto protect the metal and promote paint adhesion.NOTE 2Materials meeting the requirements of the latest revision ofU.S. Military Specification MIL-M-10578B may be used.5.4 Method 3, Acid Fluoride Deoxidizer This treatmentincludes th
18、e use of nitric or sulfuric acid with chromiumtrioxide and a fluoride. It provides a clean and uniform surfacewithout undue roughening and is effective for removinginorganic soils and any film formed during the production ofthe hot dip aluminum. The deoxidizing solution is generallyused at a tempera
19、ture of 70 to 130F (21 to 54C) (dependingon the alloy and the amount of film) and is followed by a waterrinse.NOTE 3Before applying the treatments according to Chemical Treat-ment Methods 3, 4, 5, 6 and 7, the aluminum surfaces should be freed ofgrease, oil or other foreign material by means of the
20、procedure describedin Solvent Cleaning Method 3, Chemical Treatment Method 1 or any othersuitable method.5.5 Method 4, Crystalline Phosphate TreatmentThissurface-coating method consists in reacting the aluminumsurface in a 130 to 145F (54 to 63C) (approximately) zincacid-phosphate solution containin
21、g oxidizing agents and othersalts for accelerating the coating action. The aluminum surfaceis converted to a crystalline, phosphate coating of the propertexture adapted to inhibit corrosion and increase the adherenceand durability of any applied paint film. The phosphate coatingprocess may be carrie
22、d out by immersion or spray application.The aluminum surface is converted to the phosphate coating byimmersion in the processing solution for 30 s to 4 min, or byspraying the solution for 10 s to 2 min (Note 3).5.6 Method 5, Amorphous Phosphate Treatment (see Note4)This process comprises treatment o
23、f clean aluminumsurfaces in a 90 to 125F (32 to 51C) aqueous solutioncomprising phosphoric, hydrofluoric acids and chromium tri-oxide. The aluminum surface is converted to a thin, adherent,amorphous coating, iridescent green to gray green in color,depending upon the aluminum alloy treated, which inh
24、ibitscorrosion and increases the adherence and durability of appliedpaint films. The coating process may be carried out byimmersion or spray application. The time of treatment willvary from 15 to 45 s for the spray process and 30 s to 3 min forthe immersion application (Note 3).5.7 Method 6, Carbona
25、te Chromate Treatment (see Note4)This process comprises treatment in a 160 to 180F (71 to82C) dilute solution of sodium carbonate and potassiumchromate for periods from 2 to 20 min, followed by a waterrinse. The surface is then given a final treatment in a 150 to160F (66 to 71C), 5% potassium dichro
26、mate solution fol-lowed by a final rinse. The treatment produces a thin, adherent,conversion coating on the surface, increasing the corrosionresistance of the metal and promoting paint adhesion (Note 3).5.8 Method 7, Amorphous Chromate Treatment (see Note4)This process comprises treatment of clean a
27、luminumsurfaces in aqueous chromium trioxide solutions containingsuitable accelerating agents such as fluoride-containing mate-rials. The aluminum surface is converted to an adherent,amorphous, mixed metallic oxide coating, iridescent golden tolight brown in color, which increases the corrosion resi
28、stanceand the adherence and durability of any applied paint film. Thecoating process may be carried out by immersion, spray orbrush application, at 70 to 130F (21 to 54C), in from 15 s to5 min contact time. It may be necessary to precede thistreatment with a deoxidizer as described in Method 3 (see
29、Note3).NOTE 4Most of the treatments conforming to Chemical TreatmentMethods 5, 6, and 7, comply with the requirements of the latest revisionof U.S. Military Specification MIL-DTL-5541.5.9 Method 8, Acid-Bound Resinous Treatment (see Note5)This surface treatment is based on the deposition of anacid-b
30、ound resinous film of approximately 0.3 to 0.5 mils (7.6to 12.7 m) in thickness on the aluminum surface in such amanner as to enhance the adhesion of subsequently appliedpaint coatings. The treatment is based on three primarycomponents: a hydroxyl-containing resin; a pigment capable ofreacting with
31、the resin and an acid; and an acid capable ofinsolubilizing the resin by reacting with the resin, the pigmentand the metal substrate. The aluminum surface should bepretreated by Solvent Cleaning Methods 1, 2 or 3 or ChemicalTreatment Methods 1 or 2 prior to the application of thistreatment. The film
32、 may be applied by brush, spray, or dip.Under normal conditions it shall dry sufficiently for recoatingwithin 30 min. The film has good adhesion to the metalsubstrate and promotes good adhesion of most subsequentorganic coatings to itself.NOTE 5Materials meeting the requirements of the latest revisi
33、on ofU.S. Military Specification MIL-C-15328 may be used to apply toChemical Treatment Method 8.6. Keywords6.1 hot-dip aluminum; pretreatment for painting; surfacetreatmentsD1731 09 (2014)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with a
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