EUROPEAN STANDARD EN ISO 3613 NORME EUROPEENNE EUROPAISCHE NORM ‘August 2001 Ics 25,220.20 ‘Supersedes EN 1SO 3613:1994 English version Chromate conversion coatings on zinc, cadmium, aluminium- zine alloys and zinc-aluminium alloys - Test methods (ISO. 3613:2000) ‘Couchos de conversion au chromate sur zinc, cadmium ot Chramatierdberzige aut Zink, Cadmium, Aluminium Zink aliages daluminium-zinc et do zinc aluminium - Méthodes Und Zink-Alumintum-Leglerungen - Prifvertahren (ISO essai (\SO 3813:2000} '3613:2000) This European Standard was approved by CEN on 24 June 2001. (CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European ‘Standard tho status of @ national standard without any alteration. Up-to-date lists and bibliographical references conceming such national Standards may be obtained on application to the Management Centre or to any CEN member. ‘This European Stancard exists in tnree oficial versions (English, French, German). A version in any other language made by translation Under the responsibly of a CEN member into its cwn language and notified to the Management Centra Nas the same status as (he cticial versions. ‘CEN members ate the national standards bodies of Austtia, Belgium, Czach Republic, Denmark, Finland. France. Germany. Greece, leeland, Ireland, tay, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. as EUROPEAN COMMITTEE FOR STANDARDIZATION COMITE EUROPEEN DE NORMALISATION EUROPAISCHES KOMITEF FUR NORMUNG Management Centre: re de Stassart, 36 B-1050 Brussels ©2001 CEN All rights of exploitation in any form and by any moans reserved Ret. No, EN {SO 3613:2001 E ‘worddwide for CEN national Members.(SO 3613:2000(E) Foreword ISO (the Intemational Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Intemational 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 thal committee. International organizations, governmental and non-governmental, in liaison with 1SO, also take part in the work. !SO collaborates closely with the Intemational Electrotechnical ‘Commission (IEC) on all matters of electrotechnica! standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an Intemational Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibifty that soma of the elements of this Intemational Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 3613 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings, Subcommittee SC 2, Methods of inspaction and coordination of test methods. This second edition cancels and replaces the first edition (ISO 3613:1980), which has been technically revised. ©1530-2000 — All rights reserved itiees INTERNATIONAL STANDARD ISO 3613:2000(E) Chromate conversion coatings on zinc, cadmium, aluminium-zince alloys and zinc-aluminium alloys — Test methods WARNING — This International Standard calls for the use of substances and/or procedures that can be injurious to health if adequate precautions are not taken. It refers only to technical suitability and in no way absolves elther the designer, the producer, the supplier or the user from statutory and all other legal ‘obligations relating to health and safety at any stage of manufacture or use. 1+ Scope This International Standard specifies methods for the determination of the — presence of colourless’) chromate conversion coatings; — Presence and quantity of hexavalent chromium in colourless and coloured coatings on zine, cadmium, aluminium (55 % mass fraction}-zine and zinc-aluminium (5 % mass fraction) alloys; — total chromium content per unit area on zinc and cadmium; — mass per unit area of both colourless and coloured coatings; —— satisfactory adhesion of chromate conversion coatings; — quality of chromate coating. These methods are applicable — to colourless and coloured chromate conversion coatings containing tri- and hexavalent chromium in varying proportions and produced by either chemical or electrochemical processes: — only to chromate coatings that are free from any supplementary coatings such as oil, water or solvent-based polymers or wax, 1}. The application of vary thin, colourless, practically invisible chromate conversion coatings is frequently called "passivation*, ‘hile the application of thicker, coloured chromate conversion coatings is often called "chromating*. The term passivation is not conect andi, iherefore, not recommended. (©1180-2000 — all rights reserved 12 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these Publications do not apply. However, partlas to agreements based on this International Standard are encouraged to investigate the possibilty of applying the most recent aditions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 3892:2000, Conversion coatings on metallic materials — Determination of coating mass per unit area — Gravimetric methods. 180 4520:1981, Chromate conversion coatings on electroplated zinc and cadmium coatings. 1SO 9227:1990, Corrosion tests in artificial atmospheres — Salt spray tests. 1EC 60068-2-30:1980, Environmental testing — Part 2: Tests. Test Db and guidance: Damp heat, cyclic (12 + 12 hour eyele). 3 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity 3.1 Test solution A (see 5.2). Dissolve 1 mg of diphenylcarbazide in a mixture of 60 mi glacial acetic acid and 40 m! distilled water contained in a beaker. Add 15m! of concentrated hydrochloric acid (relative density 1,18), stir and add slowly 30 ml of sodium hypechlorite solution (10% 10 15% available chlorine). Add 5 ml of hydrogen peroxide (30%) slowly with continuous stirring. Leave the solution in the open beaker for 24 h in a {ume cupboard, to allow excess chlorine to escape, before use. NOTE The solution does not deteriorate with age and therefore can be kopt in a bottle with a loosely fitting glass stopper over a period of sevoral months. 3.2 Test solution B (see 5.3), Dissolve 50 of lead acetate trihydrate [(CH,COO),Pb"3H,0] in 1 | of distilled or de-ionized water. Ensure that the PH af the solution is between 5,5 and 6,8 as prepared. If the pH of the solution is outside this range, discard the solution and oblain a new supply of lead acetate. Any white precipitate formed during the initial preparation of the solution may be dissolved by small additions of glacial acetic acid, provided that the pH is not reduced to a value below 5,5. Discard the stock solution if the white precipitate does not disappear. 3.3 Test solution C (see 5.5) Dissolve 0.4 g of diphenylcarbazide in a mixture of 20 ml acetone and 20 ml ethanol (96 %). After dissolution, add 20 mi of 75 % orthophosphoric acid solution and 20 mi of distilled water. Prepare this solution not more than 8h prior to use. 3.4 Test soluti n D (see 5.6 and 5.7). Dissolve 0,50 9 of diphenyicarbazide in 50 ml of acetone. Dilute slowly, while stirring, wit mixing can result in precipitation of diphenylearbazide).. 50 ml of water (rapid For maximum stability, store the solution under refrigeration in an amber-coloured glass bottle. {© 180 2000 - Al rights reservedCnn nnnnnnnn ee ISO 3613:2000(), 3.5 Sulfuric acid, diluted 1 +3. Slowly add 1 volume of concentrated sulfuric acid (relative density 1,84) to 3 volumes of water. 3.6 Ammonium persulfate [(NH,}2520g] 3.7 Sodium hydroxide (NaOH), (240 gf) solution. 3.8 Silver nitrate (AgNO), 17 gil solution 3.9 Potassium dichromate (K,Cr207), standard solution, Dilute to 1.000 ml 2 ml of standard volumetric potassium dichromate solution (4,9 gf). 3.10 Phosphate butter solution Dissoive 55 g of sodium dihydrogen orthophosphate monohydrate (NaHPO,-H,0) in 100 ml water. 4 Apparatus 4.1 Photoelectric absorptiometer (colorimeter), with a filter having a mean transmission of 620 nm. The absorptiometer shall be used with an absorption cell of optical path length 10 mm. 42 Spectrophotometer, with wavelength set at 540nm. The spectrophotometer shall be used with an absorption cell of optical path length 10 mm. 5 Test methods 5.1 General The test surface, prior to the following tests, shall be free of all contaminants, finger prints and other extraneous stains. If the surface is coated with thin oi, it shall be removed prior to the test by degreasing using a suitable solvent at room temperature (not exceeding 35 °C). For test purposes, the samples shall not be subjected to forced drying at temperatures in excess of 35°C. Treatment in alkaline solutions shall not be performed as chromate conversion coatings are broken down by alkalis. The test methods for a) the presence of a colourless chromate coating on zine, cadmium and aluminium-zine alloy, b) the presence of hexavalent chromium in both coloured and colourless chromate coatings, ‘c)_ the determination of hexavalent chromium content and ) the determination of total chromium content are given in 5.210 5.7. The tests shall be carried out within the following time limits: — minimum 24 h after the application of the chromate conversion coating for all tests (6.2 0 §.10); © 150 2000~ All rights reserved 3180'3613:2000(E) — maximum 3 d for tests specified in 5.2 to 6.52; — maximum 80 ¢ for tests specified in 5.6 and 5.7. The test methods for @) the determination of mass per unit area of chromate conversion coatings, b) adhesion by abrasion and ©) the evaluation of the quality of chromate layer ate given in 5.8, 5.9 and 5.10, respectively. 5.2 Test for the presence of a colourless chromate coating on zinc Apply 1 drop of test solution A (3.1) to the chromated zinc surface. The formation of a red of red-violet colour in the ‘drop shall be deemed to indicate the presence of chromate fitm. 5.3 Test for the presence of a colourless chromate coating on zinc and cadmium Place 1 drop of test solution B (9.2) on the surface to be tested. In the case of a zinc substrate, observe the appearance of the spot for 3 min. The formation of a dark or black stain at least 1 min after the application of the test solution shall be deemed to indicate the presence of a colourless chromate conversion coating. Black stain formation after more than 3 min can be indicative of the presence of supplementary coatings, such as wax or oil. In the ase of a cadmium substrate, observe the appearance of the spot for 1 min. The formation of a dark or black stain at least 5 s after the application of the test solution shall be deemed to indicate the presence of a colourless chromate conversion coating. Black stai wax or oil. formation after more than 4 min can be indicative of the presence of supplementary coatings, such as For comparison purposes, test an untreated surface similarly. Untreated zinc and cadmium surfaces or the surfaces that have been treated for chromate conversion coating but do not have continuous coating will react with the lead acetate solution to form a black stain on the untreated or bare zinc and cadmium surfaces almost immediately, within 2 s to 5, after the application of the test solution. NOTE 1 Because of the sensitivity of the method, the test is considered to be a quality control too! for the processor. Items with damaged chromate layers should not be tested by this method. NOTE 2 _Chromate conversion coatings exposed to temperatures above 60°C will have considerably reduced resistance to corrosion in the accelerated test methad (5.10), and will show black stain in less than 60's on zinc, and less than 5s on cadmiun, NOTE 3 _ No significance should be placed upon any differences in the reaction time to black spot formation between 1 min and 3min on @ zinc substrate, or between 5s and 60s on a cadmium substrate, with colourless chromate conversion Ueatment, Factors such as substrate surface texture (roughness), chromate film thickness variations (due to processing conditions), variations in the ambient temperature of the test, and precise pH control of the lead acetate sotution have an influence on the reaction time and therelore preclude any rating based upon times beyond those already stated. Similarty, the test cannot be used to compare the corrosion protection of chromate conversion coatings made from various types of chromate treatment solutions. 2) This may require special arrangements lo be made between the purchaser and the supplier. © 130 2000 — All rights raserved1SO 3613:2000(E) 5.4 Test for the presence of a colourless chromate coating on aluminium-zine (85 % mass fraction aluminium) and zinc-aluminium (5 % mass fraction aluminium) alloys Expose the test specimen for 24 h to an accelerated damp heat test in accordance with IEC 60068-2-30. The formation of a dark grey to black stain over the main part of the area shall be deemed to indicate the absence of chromate conversion coating. NOTE This test does not have any significant effect on the surtace appearance ila chromate conversion coating is present. 5.5 Test for the presence of hexavalent chromium in both colourless and coloured chromate coatings Place 1 drop to 5 drops of test solution C (3.3) on the surface to be tested. If hexavalent chromium is present, a red {o violet colour will appear within a few minutes, Ignore any colour thal appears much later, for example on drying For comparison purposes, test an untreated surface similarly. NOTE The treatment will not have any significant etfoct on the surtace appearance, 5.6 Determination of hexavalent chromium content of coloured chromate coatings 5.6.1 Preparation of calibration graph 5.6.1.1. To a series of five 250 mi volumetric flasks, add respectively 0 ml (Le. the compensation solution), 10 ml, 20 ml, 30 ml and 40 ml standard potassium dichromate solution (3.9). Add to each flask 100 ml water and 3 mi sulfuric acid solution (3.5). To one flask add 3 ml test solution D (3.4) and mix well. Exactly 2 min after the addition of test solution D, add 25 ml phosphate buffer solution (3.10), dilute to the mark and mix. Repeat this procedure with the other four flasks. 5.6.1.2 Transfer @ portion of each solution to an absorption cell and measure the absorbance in the absorptiometer (4.1) or spectrophotometer (4.2). Complete each reading within 25 min after the addition of test solution D (3.4), as the colour is not stable. Subtract the compensation solution (see 5.6.1.1) from each reading and plot the differences against micrograms of chromium per 250 mi. 5.6.2 Blank test Carry out a blank test in accordance with 5,6.3 and record the result. NOTE Test sample for blank test: 0 mi standard potassium dichromate solution + addition of reagents and test solution as described in 5.6.6.1 5.6.3 Determination 5.6.3.1 Cut.a test piece measuring about 50 mm x 100 mm from the coated item. Bring to boiling 50 ml of distilled water in a suitable vessel and totally immerse the test specimen in this. Leach for exactly min while the ‘water continues to boil, remove the specimen and rinse over the vessel. Cool the vessel and its contents to room temperature, add 3 ml of sulfuric acid solution (3.5) and mix. Transfer the contents to a 250 ml volumetric flask. Rinse the vessel twice into the flask with 10 ml to 15 ml of distilled water, add 3 ml of test solution D (3.4) and mix. Exactly 2 min after addition of the test solution D add 25 ml of phosphate buffer solution (3,10), ditute to the mark and mix, 56.3.2 Transfer a portion of the solution to an absorption cell and measure the absorbance in the absorptiometer (4.1) or spectrophotometer (4.2). Complete the reading within 25 min of the addition of test solution D (34), as the colour is not stable. Subtract the blank test reading (sce 5.6.2) tram the instrument reading and using the calibration graph (see §.6.1) convert the result into micrograms per 250 ml. 6.6.3.3 If the reading obtained falls within the portion of the calibration graph below 10 yg, repeat the determination using a larger test piece (1,5 x to 2 x the dimensions given in 5.6.3.1). © 180 2000 - All sights reserved 5- ISO 8613:2000(E) 5.6.4 Expres: n of results Determine the total surface area of coating on the test specimen, in square centimetres. Divide the hexavalent chromium content obtained in accordance wilh 5.6.3 by the surface area of the coating. The hexavalent chromium content shall be expressed in micrograms per square centimetre. 5.7 Determination of total chromium content of coloured chromate coatings 5.7.1 Preparation of calibration graph Prepare a calibration graph in accordance with 5.6.1. 5.7.2 Blank test Carry out a blank test in accordance with 5.6.2. 5.7.3 Determination 5.7.3.1 __Cuta test piece measuring about 50 mm x 100 mm from the coated item, Heat 25 ml of sulfuric acid jon (8.5) to 40 °C to 50 °C and pou jtable vessel containing the test specimen. Swirl continuously so that all surfaces are exposed to acid for 10s to 18s. Remove the test specimen, and rinse over the vessel, Dilute to about 175 ml, add about 0,1 g ammonium persulfate (3.6) and 3 ml silver nitrate solution (3.8). Then add anti- bumping granules and boil for 30 min. Cool and adjust the pH to 1,5 to 1,8 using about 20 ml sodium hydroxide solution (3.7). To measure the pH, transfer a drop to pH paper; do not immerse the paper in the solution. Transfer 10 @ 250 ml one-mark volumetric flask. Rinse the vessel twice into the flask with 10 ml to 15 ml water, add 3 ml test solution D (3.4), and mix. Exactly 2 min after addition of test solution D add 25 ml phosphate buffer solution (3.10), dilute to the mark and mix. 5.7.3.2 Transfer a portion of the solution to_an absorption cell and measure the absorbance in the absorpliometer (4.1) or spectrophotometer (4.2). Complete the reading within 25 min of the addition of test solution D (3.4) as the colour is not stable. Subtract the blank test reading (see 5.7.2) from the instrument reading, ‘and using the calibration graph (see 5.7.1), convert the result into micrograms per 250 mi. 5.7.4 Expression of results Determine the total surface area of coating on the test specimen, in square centimetres. Oivide the total chromium content obtained in accordance with 5.7.3 by the surface area of the coating. The total chromium content shall bo ‘expressed in micrograms per square centimetre. 5.8 Determination of mass per unit area of both colourless and coloured chromate coatings by gravimetric method The mass per unit area shall be determined in accordance with ISO 3892. The mass per unit area shall be expressed in milligrams per square centimetre, 5.9 Test for adhesion by abrasion Test the adhesion of the chromate by lightly rubbing the surface for about 10 strokes with white paper, such as a No. 40 Whatman filter paper or a griless, soft gum eraser. The adhesion of the coating shall be deemed satisfactory if no more than the faintest stain is visible on the paper and there is no sign of the underlying metal surface due to the removal of the coating NOTE This test method is not quantifiable. 180.2000 — Al rghsroserved