1、Designation: D 3933 98 (Reapproved 2004)Standard Guide forPreparation of Aluminum Surfaces for Structural AdhesivesBonding (Phosphoric Acid Anodizing)1This standard is issued under the fixed designation D 3933; the number immediately following the designation indicates the year oforiginal adoption o
2、r, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes the requirements for phosphoricacid anodizing of aluminu
3、m and its alloys for structuraladhesive bonding.1.2 The procedure included herein is based on the commer-cial practice of numerous agencies and organizations. Themethod may be revised or supplemented, as necessary, toinclude methods based on proven performance.1.3 The surface preparation of metal sy
4、stems used forqualification and quality-control testing of the adhesive shouldbe agreed upon between the manufacturer and the user.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standard does not purport to addres
5、s 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 applica-bility of regulatory limitations prior to use. A specific precau-tion is given in 5.5.2. Referenced Docum
6、ents2.1 ASTM Standards:2D 907 Terminology of AdhesivesD 2651 Guide for Preparation of Metal Surfaces for Adhe-sive Bonding2.2 Federal Specifications:0-0-670 Orthophosphoric Acid, Technical33. Terminology3.1 DefinitionsMany terms in this guide are defined inTerminology D 907.4. Significance and Use4.
7、1 Durable adhesive bonds between metal to metal, metalto composites can be obtained reliably only through properselection and careful control of the materials used and the stepsin the bonding process. The preparation of the metallicsubstrates to obtain surfaces with appropriate characteristics isa c
8、ritical step. Improper surface preparation can produceseemingly acceptable bonds that can degrade rapidly with time.This guide describes one method on how to properly preparealuminum surfaces can be obtained.4.2 The formation of reproducible, durable, adhesive bondsin structural assemblies requires
9、great care in the selection ofmaterials, the preparation of the surfaces of the components tobe bonded, the fit of the components, and the performance ofthe steps in the bonding process. Experience has shown thatwhen adhesively bonded aluminum surfaces which have beenprepared in accordance with this
10、 guide produce relativelyreproducible, durable bonds.5. Apparatus5.1 Locate surface preparation and drying facilities separatefrom other activities or equipment, or both, to precludecontamination by substances detrimental to adhesion.5.2 Facilities should be arranged such that parts can flowfrom the
11、 beginning of surface preparation to the primingoperation without being touched.5.3 Filters or traps, or both, should be installed for removingairborne dust, moisture, and oil from all air lines or ducts usedfor solution agitation and parts drying. Periodically check,clean, or replace filters to ens
12、ure proper operation.5.4 Surface preparation facilities should not be used forpurposes other than the preparation of parts for adhesivebonding and subsequent finishing.5.5 Equipment requirements for this process include equip-ment normally used in the chemical processing of aluminumalloys, with the
13、following special provisions:5.5.1 Racks and frames that are electrically anodic shall beconstructed of materials that will not cause corrosive reactionswith the suspension wires or clips, or the parts, during theentire process. “Picture-frame”-type racks have performedsatisfactorily.1This guide is
14、under the jurisdiction ofASTM Committee D14 onAdhesives andis the direct responsibility of Subcommittee D14.80 on Metal Bonding Adhesives.Current edition approved April 1, 2004. Published April 2004. Originallyapproved in 1980. Last previous edition approved in 1998 as D 3933 98.2For referenced ASTM
15、 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 website.3Available from U.S. Government Printing Office Superintendent of Documents,732 N
16、. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.5.2 Parts shall be attached to racks or frames with con-ductive material that anodizes, that is, aluminum or titanium inthe for
17、m of wire, hooks, springs, clips, etc.5.5.3 The phosphoric acid anodizing tank lining shall be ofsuch material that interaction between the solutions, parts,frames, racks, or clips and hangers does not interfere with theanodic process and is suitable for use as a cathode. Tanksshould be equipped wit
18、h a surface skimming device to removesurface contamination, a filtering system, and an agitationsystem for mixing the tank contents.5.5.4 Terminals for electrical current shall be designed andpositioned such that parts cannot be “burned.”5.5.5 The electrical system used during a single-rack anodicpr
19、ocess shall be adequate for producing 10-V dc and maintain-ing any set voltage within 61-V dc.5.5.6 The electrical system used during a multiple-rackprocess shall be adequate for producing 15-V dc and maintain-ing any set voltage within 61-V dc.5.5.7 Rinse tanks should be placed adjacent to processi
20、ngtanks in such a manner that parts can be easily and quicklymoved from one solution to another so that the parts will notbecome dry during successive steps of the process.5.5.8 Incoming solution makeup water and rinse water shallcontain not more than the “recommended upper limit” forfluoride and no
21、t more than the “highest desirable level” ofdissolved chemicals based on American Chemical Societystandards for deionized or distilled water, or both (1.7 ppmfluoride, 500 ppm total dissolved solids, etc.) except that:5.5.8.1 Chloride shall not exceed 25 ppm.5.5.8.2 pH shall be between 5.5 and 8.0.N
22、OTE 1Most regionally distributed potable water will meet theserequirements.5.5.8.3 If the above requirements cannot be met, the incom-ing water shall be deionized and maintained within thefollowing limits:(a) Total dissolved solids shall not exceed 150 ppm.(b) pH shall be between 5.5 and 8.0.6. Manu
23、facturing6.1 Parts shall be racked or suspended from frames such thatthey all have firm, reliable electrical contact with the anodeconnections, so that the parts do not contact each other and thatrinse water contacts all surfaces and drains freely.6.2 Take the utmost care that the parts are not touc
24、hed at anytime during the entire process, such as touching of adjacentparts, the rack or supporting frame, or any other item, since thesurfaces and the phosphoric acid anodic coating are susceptibleto contamination or physical damage prior to the applicationand cure of the primer.6.3 If it becomes n
25、ecessary to handle or touch parts, cleanwhite gloves should be used and contact should be limited tosurfaces not to be adhesively bonded.6.4 If parts become contaminated, either prior to or subse-quent to anodizing, corrective action shall be accomplished byreprocessing, beginning with alkaline clea
26、ning.6.5 To ensure solution homogeneity, agitate immediatelyprior to process use and after every addition of water orchemicals. (WarningSolutions used in this process arecorrosive and toxic. Avoid breathing solution mists or vapors.Do not allow solutions to get on the eyes, on the skin, or onclothin
27、g.)6.5.1 Consult Industrial Hygiene for safety precautions.6.6 Control the time interval between withdrawal fromprocessing solutions and rinsing so that there is no drying ofthe solution on the details.6.7 Parts must be water-break-free following rinsing afteralkaline cleaning, after deoxidizing, an
28、d after anodizing.7. Procedure7.1 Perform the surface preparation process in a continuousoperation as detailed in the flow chart, Fig. 1.7.2 Complete all fabrication processes, inspections, prefit,etc. before the start of the preparation cycle.7.3 Complete all “hand work” before solvent cleaning.7.4
29、 Once racked for alkaline cleaning, parts shall not betouched by anything except the applicable processing solutionand rinse waters, until the parts are dried after primer applica-tion (5.2).7.5 The “wet” processing steps, from alkaline cleaningthrough drying after phosphoric acid anodizing, should
30、beperformed in one continuous uninterrupted sequence of pro-cesses, with the parts not drying at any time until the ovendrying after the rinse following phosphoric acid anodizing.7.5.1 Should the parts become delayed prior to anodizingduring this wet processing, hold the parts in the applicablerinse
31、 tank.7.5.2 There shall be no holding of parts in the processingsequencing after anodizing.7.6 Should the electric current fail or otherwise be inter-rupted during the phosphoric acid anodizing, anodizing may becontinued for an additional 20 to 25 min, if the potential can bereestablished within 2 m
32、in. If the potential cannot be reestab-lished within 2 min, then rinse and reprocess starting with thedeoxidizer.7.7 Apply adhesive primer within 72 h after oven dryingfollowing the phosphoric acid anodizing. Parts should be heldin a limited contamination area prior to priming and should notbe handl
33、ed (5.2). However, it is most desirable to prime partsas soon as possible to minimize the possibility of inadvertentcontamination.7.8 Rinse Requirements:7.8.1 Rinsing may be by spray or immersion. Single sprayor double counter-current immersion rinsing are commonlyused.7.8.2 Feed water to rinse oper
34、ations may be direct fromsource water in accordance with 5.5.8 or from any subsequentrinse operation, except that acid rinse waters shall not be fedinto alkaline rinse waters.7.8.3 Final immersion rinse water after alkaline cleaning,deoxidizing, and anodizing shall not exceed 1000 ppm totaldissolved
35、 solids above that of the incoming rinse water (5.5.8).When double independent feed or double-counter currentimmersion rinse is used, the first rinse after anodizing shall notexceed 5000 ppm, and the time in first rinse shall not exceed 2min from time of starting immersion to complete withdrawal.Imm
36、ersion rinse tank(s) used for anodize rinse shall be used foranodize rinse only.D 3933 98 (2004)27.8.4 Agitate immersion rinse tanks during rinsing to aidrinsing and prevent stratification.7.8.5 Allowable concentration limits may exceed normalcontrol limits for the first 30 s of rinsing.8. Quality A
37、ssurance Provisions8.1 Part Inspection During ProcessingParts should beinspected during the continuous processing, as noted in Fig. 1.8.1.1 Water-Break Inspection:8.1.1.1 On removal from rinses, cleaned parts shall passwater-break inspection as indicated by maintenance of acontinuous film of water o
38、n the surface for not less than 30 s.8.1.1.2 Parts failing water-break inspection shall be repro-cessed through the applicable cleaning operation until thesurface can maintain the continuous film of water.8.1.2 Phosphoric Acid Anodic Coating Inspection:8.1.2.1 After anodizing and during rinsing and
39、draining,there shall be no evidence of a water break. There shall be nostains, streaks, discoloration, or residue on surfaces of anod-ized parts after rinsing (5.5.8).8.1.2.2 The anodic coating should be continuous, smooth,uniform in appearance, and when examined visually, should befree from discont
40、inuities, such as scratches, breaks, burnedareas, and areas that are not anodized. Small irregularities atpoints of electrical contact are acceptable. If practical, putelectrical contacts in areas that will not be bended or in a trimtab that will be removed from the finished part.8.1.2.3 The anodize
41、d surfaces shall pass the followingpolarized color change examination:(a) Illuminate the surface at a low angle using any white ornear-white lamp.NOTE 1Experience has proved nonsilicated cleaners to be preferable when reprocessing might be involved.NOTE 2A single-rack facility is one with a single a
42、node rack between each set of cathodes. A multi-rack has two or three anode racks between eachset of cathodes.FIG. 1 Process Flow ChartD 3933 98 (2004)3(b) Observe the reflected light at a low angle (010) byplacing a light-polarizing filter either between the light and thesurface or between the surf
43、ace and the observer.(c)An anodized surface shall display an“ interference color,”which should change to another color when the filter is rotated90 (for example, from purple to yellow green).(d) Rotation of the filter is necessary since some colors maybe pale and not discernible until another color
44、is observed byrotation of the filter.(e) Different pieces of aluminum alloy anodized under thesame loads may show different colors through the polarizingfilter due to differences in alloy composition, metallurgicalcondition, and specific anodizing conditions at different posi-tions in the tank durin
45、g anodizing. The colors most frequentlyseen are purple, yellow, blue, and green hues.( f) All surfaces to be adhesively bonded shall exhibit thecolor changes noted above. Abrupt differences in color of localareas, except at electrical contact points, from the backgroundcolor are not acceptable. Caus
46、es of such differences may befingerprints, abrasion, or other contamination.NOTE 2The color change may be difficult or impossible to detect onsurfaces that have been etched by marking ink, roughened by machining,sanding, deburring, etc., or uninspectable because of shape. In these cases,the presence
47、 of color on tool tabs or on the opposite surface, or onundisturbed surfaces, may be evidence that the surface is acceptablyanodized.(g) Parts not passing the polarized color change test shall berejected or reprocessed starting with the alkaline cleaning step.8.2 Makeup and Process Control of Proces
48、sing Solutions:8.2.1 Alkaline CleanerMakeup, replenishment, and re-placement of alkaline cleaning solutions should be developedto produce effective processing.8.2.2 DeoxidizerMakeup, replenishment, and replace-ment of deoxidizer should be defined to produce effectiveprocessing. The sulfuric acid-sod
49、ium dichromate etch (MethodG for Aluminum Alloy in Guide D 2651) has been an effectiveetch.8.2.3 Phosphoric Acid Anodizing Solution:8.2.3.1 Initial Tank Makeup(a) Fill the tank approximately three-quarters full of cleanwater (5.5.8).(b) Agitate the water and slowly add 7 parts of phosphoricacid (AA55820, Class I, 85 % phosphoric acid) for each 100parts of final solution.(c) Bring mixture to operating level of the tank with cleanwater (5.5.8) and mix thoroughly.8.2.3.2 MaintenanceMaintain the phosphoric acid con-centration and operating conditions as specified in Tabl
