1、Designation: D3933 98 (Reapproved 2010)Standard Guide forPreparation of Aluminum Surfaces for Structural AdhesivesBonding (Phosphoric Acid Anodizing)1This standard is issued under the fixed designation D3933; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of revision, the 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. Scope1.1 This guide describes the requirements for phosphoricacid anodizing of aluminum a
3、nd 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 syste
4、ms 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 address a
5、ll 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 Document
6、s2.1 ASTM Standards:2D907 Terminology of AdhesivesD2651 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 D907.4. Significance and Use4.1 Dura
7、ble 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 critica
8、l 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 great
9、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 guide
10、 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 begin
11、ning 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 ensure pr
12、oper 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 follow
13、ing special provisions:1This guide is under the jurisdiction ofASTM Committee D14 onAdhesives andis the direct responsibility of Subcommittee D14.80 on Metal Bonding Adhesives.Current edition approved Oct. 1, 2010. Published October 2010. Originallyapproved in 1980. Last previous edition approved in
14、 2004 as D3933 98 (2004).DOI: 10.1520/D3933-98R10.2For 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 website.3Available
15、from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.5.1 Racks and frames that are e
16、lectrically 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.5.5.2 Parts shall be attached to racks or frames with con-ductive material th
17、at anodizes, that is, aluminum or titanium inthe form 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 suitab
18、le for use as a cathode. Tanksshould be equipped with 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
19、electrical system used during a single-rack anodicprocess 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
20、.7 Rinse tanks should be placed adjacent to processingtanks 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 t
21、han the “recommended upper limit” forfluoride and not 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 exc
22、eed 25 ppm.5.5.8.2 pH shall be between 5.5 and 8.0.NOTE 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
23、 150 ppm.(b) pH shall be between 5.5 and 8.0.6. Manufacturing6.1 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.
24、6.2 Take the utmost care that the parts are not touched 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 a
25、pplicationand cure of the primer.6.3 If it becomes necessary 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 accom
26、plished byreprocessing, beginning with alkaline cleaning.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 sol
27、utions to get on the eyes, on the skin, or onclothing.)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 r
28、insing afteralkaline cleaning, after deoxidizing, and 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
29、Complete all “hand work” before solvent cleaning.7.4 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 cleaningthr
30、ough drying after phosphoric acid anodizing, should 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 w
31、et processing, hold the parts in the applicablerinse 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
32、min, if the potential can bereestablished within 2 min. 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 contam
33、ination area prior to priming and should notbe handled (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 rin
34、sing are commonlyused.7.8.2 Feed water to rinse operations 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, an
35、d anodizing shall not exceed 1000 ppm totaldissolved solids above that of the incoming rinse water (5.5.8).D3933 98 (2010)2When 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 ex
36、ceed 2min from time of starting immersion to complete withdrawal.Immersion rinse tank(s) used for anodize rinse shall be used foranodize rinse only.7.8.4 Agitate immersion rinse tanks during rinsing to aidrinsing and prevent stratification.7.8.5 Allowable concentration limits may exceed normalcontro
37、l limits for the first 30 s of rinsing.8. Quality Assurance 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 indi
38、cated by maintenance of acontinuous film of water on 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 Inspect
39、ion:8.1.2.1 After anodizing and during rinsing and 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
40、 when examined visually, should befree from discontinuities, 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
41、 removed from the finished part.8.1.2.3 The anodized surfaces shall pass the followingpolarized color change examination:NOTE 1Experience has proved nonsilicated cleaners to be preferable when reprocessing might be involved.NOTE 2A single-rack facility is one with a single anode rack between each se
42、t of cathodes. A multi-rack has two or three anode racks between eachset of cathodes.FIG. 1 Process Flow ChartD3933 98 (2010)3(a) Illuminate the surface at a low angle using any white ornear-white lamp.(b) Observe the reflected light at a low angle (010) byplacing a light-polarizing filter either be
43、tween the light and thesurface or between the surface 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 m
44、aybe pale and not discernible until another color 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 co
45、nditions at different posi-tions in the tank during 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,
46、 from the backgroundcolor are not acceptable. Causes 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 uninspect
47、able because of shape. In these cases,the presence 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 clea
48、ning step.8.2 Makeup and Process Control of Processing 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
49、produce effectiveprocessing. The sulfuric acid-sodium dichromate etch (MethodG for Aluminum Alloy in Guide D2651) 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-centr
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