1、Designation: D 1730 03Standard Practices forPreparation of Aluminum and Aluminum-Alloy Surfaces forPainting1This standard is issued under the fixed designation D 1730; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These practices cover four types of tre
3、atment for prepa-ration of aluminum and aluminum-alloy surfaces for painting,as follows:1.1.1 Type ASolvent Cleaning.1.1.2 Type BChemical Treatments.1.1.3 Type CAnodic Treatments.1.1.4 Type DMechanical Treatments. These four typescover a number of procedures, as described herein.1.2 Variations in su
4、rface treatment produce end conditionswhich differ, and which do not necessarily yield identicalresults when paints are applied. Service conditions will dictatethe type of surface preparation that should be selected, al-though the quality produced by any individual method mayvary with different allo
5、ys.1.3 This standard may involve hazardous materials, opera-tions, 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-m
6、ine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 609 Practice for Preparation of Cold-Rolled Steel Panelsfor Testing Paint, Varnish, Conversion Coatings and Re-lated Coating Products22.2 Military Standards:MIL-C-5541 Chemical Conversion Coating
7、s on Aluminumand Aluminum Alloys33. Type ASolvent Cleaning3.1 Solvent cleaning does not disturb the natural oxide filmon the metal and may prove adequate for some applications,such as ambient indoor or very mild service conditions. Threemethods may be employed, as follows:3.1.1 Method 1, Manual Swab
8、bing or Dip-Washing, with asolvent such as mineral spirits or high-flask solvent naphtha.With this method it is extremely difficult to prevent accumu-lation of contaminants on the swab or in the solvent. Thismethod is only recommended when other treatments areimpractical.3.1.2 Method 2, Solvent Spra
9、y Cleaning, in accordance withMethod A, Procedure 1 of Practice D 609.3.1.3 Method 3, Vapor Degreasing, in special equipmentemploying trichloroethylene vapor, in accordance with MethodA, Procedure 2 of Practice D 609.4. Type BChemical TreatmentsNOTE 1Materials and procedures employed in these method
10、s 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 hexavalentchromium is a known carcinogen.4.1 Method 1, Alkaline CleanersAlkaline solutions, suchas caus
11、tic soda, etch the metal, thus destroying the naturaloxide film. They are followed by an acid treatment, preferablynitric acid or phosphoric acid. They shall not be used onassembled structures. Inhibited alkaline cleaners are sometimesemployed as a pretreatment to remove grease and oil prior to anac
12、id treatment. Inhibited alkaline cleaners do not etch thesurface. They are not generally recommended unless followedby a conversion treatment, such as described in Methods 4, 5,6, or 7.4.2 Method 2, Sulfuric Acid, Chromium Trioxide EtchThis treatment provides a clean and uniform surface withoutundue
13、 etching, and is effective for removing oil and waterstains and any film formed during heat-treatment. The etchingsolution is prepared by adding 1 gal (3.78 L) of concentratedsulfuric acid and 45 oz (1.28 kg) of chromium trioxide to 9 gal(34 L) of water. It is used at a temperature of 160 to 180F (7
14、1to 82C) (depending on the alloy and the amount of film) forabout 5 min and is followed by a water rinse. This treatmentproduces a passive surface suitable for painting under mild tointermediate exposure conditions and where clear finishes areto be applied.1These practices are under the jurisdiction
15、 of ASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.07 onChromate Conversion Coatings.Current edition approved Sept. 10, 2003. Published Sept. 2003. Originallyapproved in 1960. Last previous edition approved in 1998 as D 1730-67 (1998).2Annua
16、l Book of ASTM Standards, Vol 06.01.3Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-50981Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 Method 3, Alcoholic
17、 Phosphoric Acid CleanerThistreatment involves the use of an aqueous solution of phospho-ric acid (10 to 15 volume %) with alcohol or other organicsolvents, together with wetting agents, emulsifying agents, etc.The solution may be applied by swabbing or dipping at roomtemperature (70 to 90F (21 to 3
18、2C), and should be allowedto remain on the surface for several minutes, followed bythorough rinsing with clean water. A very thin phosphate filmis formed which tends to protect the metal and promote paintadhesion under mild to intermediate exposure conditions.NOTE 2U.S. Military Specification MIL-M-
19、10578B describes a treat-ment of this type.4.4 Method 4, Crystalline Phosphate TreatmentThissurface-coating method consists in reacting the aluminumsurface in a zinc-acid-phosphate solution containing oxidizingagents and other salts for accelerating the coating action. Thealuminum surface is convert
20、ed to a finely crystalline, phos-phate coating of the proper texture adapted to inhibit corrosionand increase the adherence and durability of any applied paintfilm. It is recommended for product finishes. The phosphatecoating process may be carried out by immersion or sprayapplication. The aluminum
21、surface is converted to the phos-phate coating by immersion in the processing solution for 30 sto 4 min at 125 to 140F (51 to 60C), or by spraying thesolution for 10 s to 2 min at 125 to 160F (51 to 71C).NOTE 3Before applying the treatments according to Methods 4, 5, 6,and 7 of Type B, the aluminum
22、surfaces should be freed of grease, oil, orother foreign material by means of the procedure described in Method 3of Type A, Method 1 of Type B, or any other suitable method.NOTE 4This treatment complies with the requirements of U.S. Fed-eral Specification TT-C-490.4.5 Method 5, Amorphous Phosphate T
23、reatmentThis pro-cess comprises treatment of clean aluminum surfaces in awarm (95 to 130F (35 to 54C) aqueous solution comprisingphosphoric, and hydrofluoric acids, chromium trioxide or asolution thereof. The aluminum surface is converted to a thin,adherent, amorphous coating, iridescent green to gr
24、ay-green incolor, depending upon the aluminum alloy treated, whichinhibits corrosion and increases the adherence and durability ofapplied paint films. This method is recommended for use underthe more severe conditions of service, and for product finishes.The coating process may be carried out by imm
25、ersion or sprayapplication. The time of treatment will vary from 15 to 45 s forthe spray process, and from 30 s to 3 min for the immersionapplication (see Note 3 and Note 5).NOTE 5Most of the treatments conforming to Methods 5, 6, and 7 ofType B comply with the requirements of U. S. Military Specifi
26、cationMIL-C-5541.4.6 Method 6, Carbonate Chromate TreatmentThis pro-cess comprises treatment in a hot (180 to 190F (82 to 88C)dilute solution of sodium carbonate and potassium chromatefor periods from 2 to 20 min, followed by a water rinse. Thesurface is then given a final treatment in hot 5% potass
27、iumdichromate solution, followed by a final rinse. The treatmentproduces a thin, adherent, conversion coating on the surface,increasing the corrosion resistance of the metal and promotingpaint adhesion. This method is recommended for use under themore severe conditions of service and for product fin
28、ishes (seeNote 3 and Note 5).4.7 Method 7, Amorphous Chromate TreatmentThis pro-cess comprises treatment of clean aluminum surfaces inaqueous chromium trioxide solutions containing suitable ac-celerating agents such as fluoride-containing materials. Thealuminum surface is converted to an adherent, a
29、morphous,mixed metallic oxide coating, irridescent golden to light-brownin color, which increases the corrosion-resistance and theadherence and durability of any applied paint film. Thismethod is recommended for use under the more severeconditions of service and for product finishes. The coatingproc
30、ess may be carried out by immersion, spray, or brushapplication, at room temperature (70 to 90F (21 to 32C), infrom 15 s to 5 min contact time (see Note 3 and Note 5).4.8 Method 8, Acid-Bound Resinous Treatment (see Note6)This surface treatment involves the use of a suitablyapplied acid-bound resino
31、us film of approximately 0.3 to 0.5mils (7.6 to 12.7 m) thickness. The treatment is based on threeprimary components: a hydroxyl-containing resin; a pigmentcapable of reacting with the resin and an acid; and an acidcapable of insolubilizing the resin by reacting with the resin,the pigment, and the m
32、etal substrate. The aluminum surfaceshould be prepared by Methods 1, 2, or 3 of Type A (seeSection 3) or chemical treatments, Type B, 4.1 or 4.2 prior tothe application of this treatment. The film may be applied bybrush, spray, or dip. Under normal conditions it should drysufficiently for recoating
33、within 30 min; and within8hitshould not be softened by organic solvents commonly used inpaint coatings. The film has good adhesion to the metalsubstrate and promotes good adhesion of most subsequentorganic coatings to itself. This method is recommended forsevere service conditions, particularly on f
34、abricated structures,either in the shop or in the field.NOTE 6Materials meeting the requirements of U.S. Military Specifi-cation MIL-P-15328b may be used to apply Method 8 of Type B.5. Type CAnodic Treatments (see Note 7)5.1 Anodic treatment in either sulfuric acid or chromiumtrioxide electrolyte wi
35、ll provide a protective and inert oxidecoating which increases the corrosion-resistance of the metaland promotes paint adhesion. It is recommended where maxi-mum corrosion-resistance by the treatment itself is desired.Anodic treatments should not be used on assemblies ofdissimilar metals. The two pr
36、ocedures are as follows:NOTE 7Treatments conforming to Methods 1 and 2 of Type C complywith the requirements of U.S. Military Specification MIL-A-8625.5.2 Method 1, Sulfuric Acid Anodic This treatment con-sists in making the part the anode in a 15% sulfuric acidelectrolyte (by weight) and applying c
37、urrent at a potential ofabout 16 to 18 V and a current density of 12 A/ft2until desiredthickness of coating is obtained. After rinsing in cold water, thecoating is sealed for 10 min by treatment in a boiling solutionof 5% potassium dichromate. This method is not recommendedwhere danger of acid entra
38、pment is encountered.5.3 Method 2, Chromium Trioxide Anodic This treatmentconsists in making the part the anode in a 10 weight %D1730032chromium trioxide electrolyte at a temperature of 100F (38C)and applying a potential of 40 V for a period of 30 to 60 min.After first rinsing in cold water, the coa
39、ting is finally rinsed inwater at 150F (66C) minimum, and dried; an optional finalsealing treatment to obtain maximum protection is obtained byimmersion in a solution containing 0.01 g chromium trioxideper litre of water (0.0013 or 1 gal) at a temperature of 208 to212F (98 to 100C) for 5 min.6. Type
40、 DMechanical Treatments6.1 Method 1, Hand or Power Wire-Brushing, or otherabrasive treatment. Wire-brushing, either by hand or power,roughens the surface of the metal and mechanically improvesthe anchorage for superimposed paint films. The disadvantagesare that the natural oxide film on the metal is
41、 disrupted and oilor grease films and other foreign matter are not completelyremoved.6.2 Method 2, Sandblasting, where employed on aluminumor its alloys, must be carried out at relatively low pressures andwith a fine silica sand. It roughens the surface and mechani-cally improves the anchorage for p
42、aint films, but destroys thenatural oxide film on the metal. Where used, it should befollowed by an inhibitive chemical treatment.7. Keywords7.1 aluminum; pretreatment for painting; surface treatmentASTM International takes no position respecting the validity of any patent rights asserted in connect
43、ion with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsibl
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45、ideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 B
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