1、 Reference number ISO/TR 16689:2012(E) ISO 2012TECHNICAL REPORT ISO/TR 16689 First edition 2012-05-01 Anodizing of aluminium and its alloys Experimental research on possible alternative sealing quality test methods to replace the phosphoric acid/chromic acid immersion test Evaluation of correlations
2、 Anodisation de laluminium et ses alliages Recherche exprimentale sur les mthodes alternatives possibles dessai de qualit de colmatage pour remplacer lessai dimmersion dans lacide phosphochromique valuation des corrlations ISO/TR 16689:2012(E) COPYRIGHT PROTECTED DOCUMENT ISO 2012 All rights reserve
3、d. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester
4、. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2012 All rights reservedISO/TR 16689:2012(E) ISO 2012 All rights reserved iiiContents Page Foreword iv Introduction . v 1 Scop
5、e 1 2 Literature research 2 2.1 General . 2 2.2 Acidified sulfite test (Kape test) . 2 2.3 Acetic acid/sodium acetate solution test 2 2.4 Chromic/phosphoric acid solution test . 3 2.5 Sulfuric acid solution test. 4 3 Materials and experimental 4 3.1 Anodizing . 4 3.2 Sealing 4 3.3 Measurements of se
6、aling quality . 5 4 Results 7 4.1 Masking of cut surfaces 7 4.2 Bare aluminium and dissolution in the dissolution tests . 7 4.3 Hot sealing . 7 4.4 Cold sealing (two step) . 13 4.5 Nickel-based medium temperature sealing 17 4.6 Nickel-free medium temperature sealing 21 5 Discussion . 24 6 Conclusion
7、 . 26 Annex A (Informative) Qualanod working group report . 27 Bibliography 30 ISO/TR 16689:2012(E) iv ISO 2012 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Inter
8、national Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison wit
9、h ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technica
10、l committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. In exceptional circum
11、stances, when a technical committee has collected data of a different kind from that which is normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is e
12、ntirely informative in nature and does not have to be reviewed until the data it provides are considered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identi
13、fying any or all such patent rights. ISO/TR 16689 was prepared by Technical Committee ISO/TC 79, Light metals and their alloys, Subcommittee SC 2, Organic and anodic oxidation coatings on aluminium. ISO/TR 16689:2012(E) ISO 2012 All rights reserved vIntroduction The chromic/phosphoric acid solution
14、(CPA) test is the main test used internationally to assess the quality of sealing of anodic oxidation coatings on aluminium. The method is described in ISO 3210 1 , ASTM B680 2 , EN 12373-6 3and EN 12373-7 4 . ISO 7599 5and EN 12373-1 6designate it to be the referee test, as do the voluntary standar
15、ds of Qualanod 7and the AAMA (American Architectural Manufacturers Association) 8 . The CPA test was originally proposed by two workers at Alcoa, J. H. Manhart and W. C. Cochran, in the early 1970s 9 . They compared it for hot-water sealing with various simple laboratory tests including other acid d
16、issolution tests, some of which were in regular use at that time and were described in ISO 2932 10 . Since the adoption of the CPA test, practical experience has revealed that low-coating mass loss is an indication of good sealing quality and of the ability of the coating to resist staining and bloo
17、ming in many types of service. There is mounting concern in Europe over the use of this test because the test solution contains hexavalent chromium Cr(VI) which is a human carcinogen via inhalation. Chromic acid was included, 2010-12-15, in The European Chemicals Agency candidate list of substances
18、of very high concern for authorization. Special authorization will have to be obtained for the use of such substances in every application. In 2007 Qualanod initiated a study to identify potential alternative tests. It was decided to restrict this to acid dissolution tests because it was expected th
19、at they would behave in a manner most similar to the CPA test. A list of criteria was drawn up for alternative tests to be assessed against. These criteria included ones that would favour easy-to-use immersion tests. The technical literature was reviewed and a shortlist of tests produced. The next s
20、tage was to carry out experimental work to determine whether the alternative tests were comparable to the CPA test for a range of sealing methods. Sapa Technology offered to undertake this project. Sapa found that neither of the acid immersion tests evaluated were suitable alternatives to the CPA te
21、st. This was because they responded very differently depending on the sealing method. It is believed that the response of any immersion test is dependent on the solution composition. Sapa also found that the admittance test was good at distinguishing sealing quality for all the sealing methods. Howe
22、ver, admittance is a property of the whole of the anodized coating whereas the CPA test is surface-specific, providing a prediction of the likelihood of surface degradation during service. This Technical Report contains an edited version of Sapa Technology technical report D09-0179 11 . It is believ
23、ed that future investigations should focus on finding a test method that will enable the prediction of superficial, cosmetic degradation during exposure to the weather. This would not include the ability of an anodized coating to protect the aluminium from pitting corrosion, which can already be ass
24、essed using a salt spray test. Rather, it would assess the susceptibility to weathering effects such as staining, blooming, chalking, resmutting and iridescence. TECHNICAL REPORT ISO/TR 16689:2012(E) ISO 2012 All rights reserved 1Anodizing of aluminium and its alloys Experimental research on possibl
25、e alternative sealing quality test methods to replace the phosphoric acid/chromic acid immersion test Evaluation of correlations 1 Scope This Technical Report contains data from an evaluation of candidates to replace the chromic/phosphoric acid solution (CPA) test for the quality of sealing of anodi
26、c oxidation coatings on aluminium. Following a review by Qualanod (see Working Group report in Annex A), it was agreed with Sapa Technology that the candidate tests for evaluation would be as follows: acetic acid/sodium acetate solution (AASA) test as described in ISO 2932 10 , a method used in the
27、1970s; sulfuric acid solution (SA) test as described by Manhart and Cochran 9 . The evaluation consists of a comparison of the candidates with the CPA (EN 12373-6 3 ), dye absorption (EN 12373-4 12 ) and admittance tests (EN 12373-5 13 ) using four different sealing methods: hot-water sealing; cold
28、sealing; medium-temperature (midtemp) sealing using a nickel-containing solution; midtemp sealing using a nickel-free solution. An immersion test based on the CPA test, but without the inclusion of chromic acid, was excluded due to the similarity with the SA test. The scope of the work to develop a
29、new phosphoric acid method was considered too comprehensive for this project. In general, the sealed coating (pores filled by hydration) loses mass and thickness linearly with dissolution time. Different sealing methods (or sealing conditions of time, temperature, pH, composition of sealing solution
30、) result in different pore-filling material with differences in resistance to acid dissolution. When considering replacing the CPA test with an alternative acid dissolution test, there are some criteria for a new test. If possible, the response to the test should be similar for different sealing met
31、hods, i.e. it should be possible to use the same standard even if the sealing method is different. There should be a significant difference in the mass loss for a good and a bad sealing. ISO/TR 16689:2012(E) 2 ISO 2012 All rights reserved2 Literature research 2.1 General A comprehensive survey of th
32、e methods of testing the sealing quality of anodic coatings was given by Manhart and Cochran 9and by Kape 14in the 1970s. A more recent survey was made in 1987 by Wernick and al. 15where the main acid dissolution tests are: acidified sulfite test (Kape test); AASA test; CPA test. These tests are exp
33、lained below, see 2.2 to 2.4. In Figure 1 is shown the correlation of several acid dissolution tests with sealing time for sulfuric acid coatings published by Manhart and Cochran 9 . Note that the curves generally exhibit the same shape with a difference in the absolute value of the mass loss. The t
34、hickness of the anodic oxide is about 25 m (estimated from given anodizing conditions). 2.2 Acidified sulfite test (Kape test) The test solution is a mixture of sodium sulfite, acetic acid and sulfuric acid at 90 C to 92 C and pH 2,5 such that sulfur dioxide is evolved but mainly retained in solutio
35、n. Test solution: 1 000 ml deionized water to which have been added glacial acetic acid (20 ml/l to 40 ml/l) to give a pH of 3,6 to 3,8 followed by 5 N sulfuric acid (10 ml/l to 15vml/l) to give a pH of 2,5 at room temperature. A predip is made 10 min in 50 % by volume nitric acid at room temperatur
36、e. The mass of the sample is assessed before predip, after predip and after immersion in test solution. Immersion of the sample for 20 min. Note that care should be taken such that the solution temperature does not at any time exceed 92 C or the sulfur dioxide dissolved in the solution will be boile
37、d off. For a coating of good quality the loss of mass between the first and second weighing is negligible (a significant difference indicates an excessively porous coating). Assessment of total mass loss is made using the mass loss between the second and third weighings. A maximum mass loss 20 mg/dm
38、 2is permitted 15(not specified in the standard). The test is described in the standard ISO 2932 10which was withdrawn in 1991. 2.3 Acetic acid/sodium acetate solution test This sealing quality test was made according to standard ISO 2932 10 . The method was used in the 1970s but the standard was wi
39、thdrawn in 1991 being replaced with the CPA test. The test solution is a mixture of 100 ml/l acetic (glacial) acid, 0,5 g/l sodium acetate in deionized water at pH 2,3 to 2,5. Renewed solution after each test is recommended. Not more that 3 dm 2surface area of immersed sample per litre of solution.
40、Non-anodized areas are not taken into account when calculating the surface area since the solution only slightly attacks bare metal (not more than 0,05 mg/cm 2 ), unless the bare areas exceeds 5 % of the total surface area of the sample. During immersion, 15 min, the solution is maintained at boilin
41、g point. A maximum mass loss of 20 mg/dm 2is permitted 15 . Furneaux and Wood pointed out that this test might be less suitable for other sealing methods than conventional hot sealing (e.g. nickel-based cold sealing) 16 . ISO/TR 16689:2012(E) ISO 2012 All rights reserved 3Key y mass loss, expressed
42、in mg/dm 2(log scale) x sealing time, expressed in minutes (log scale) 1 15 % H 2 SO 4 2 2 % CrO 3 5 % H 3 PO 43 acetic acid 4 6 % citric acid 5 acidified Na 2 SO 36 20 % HNO 3NOTE This figure is reproduced with permission from the National Association for Surface Finishing, 1155 15th St., NW, Suite
43、 500, Washington, DC 20005 USA. Figure 1 Correlation of several acid dissolution tests with sealing time for sulfuric acid coatings 92.4 Chromic/phosphoric acid solution test This test was originally proposed by Manhart and Cochran in 1971 9and was then adopted as the general referee mass loss test
44、previously described by ISOv3210 1 . The sealing quality is evaluated with a mass loss test today according to EN 12373-6 3 . The mass loss test is destructive and frequently used as a complement to the dye spot test (EN 12373-4 12 ). The better the sealing, the lower the mass loss in this test. The
45、 specifications on the mass loss vary depending on the application, even though for normal applications a mass loss of less then 30 mg/dm 2is needed for approval according to Qualanod 7 . The test solution is a mixture of 2 % by mass chromic acid and 5 % by mass phosphoric acid, operated at 37,8 C f
46、or 15 min the same solution is used at higher temperature for determination of oxide density (EN 12373-2 17 ). ISO/TR 16689:2012(E) 4 ISO 2012 All rights reservedNote the drying procedures associated with the weighing. Prior to weighing the sample is: degreased for 30 s in a suitable organic solvent
47、 (e.g. ethanol); left to dry 5 min in ambient atmosphere; placed in a drying oven pre-heated to 60 C for 15 min; left to cool for 30 min over silica gel in a closed desiccator. When this test is performed in a production line however the drying procedures are probably always simplified (i.e. no dryi
48、ng in oven and no cooling down in desiccator). This sealing test is sometimes combined with a 10 min predip in an aqueous solution containing (470 15) g/l nitric acid (EN 12373-7 4 ), specified according to Qualanod 7 . The test solution should not be used for more than 10 dm 2surface area of immers
49、ed sample per litre of solution. The result is similar as with Kape and AASA tests but with greater mass losses (sulfuric acid anodized coatings) 14 . Some of the mentioned advantages 9with the CPA test are the stability, convenient operating temperature, no attack of uncoated metal, a convenient test period and no unpleasant odour. Thickness loss and mass loss occur at the same rate. 2.5 Sulfuric acid solution te
