1、ASD STANDARD NORME ASD ASD NORM prEN 4195 Edition P1 November 2005 PUBLISHED BY THE AEROSPACE AND DEFENSE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATIONGulledelle 94 - B-1200 Brussels - Tel. + 32 2 775 8126 - Fax. + 32 2 763 3565 - www.asd-stan.orgICS: Descriptors: ENGLISH VERSION Aerospace seri
2、es Paints and varnishes Test method for determination of chromate leaching Srie arospatiale Peintures et vernis Test de lixiviation de chromate Luft- und Raumfahrt Anstrichstoffe Chromatauslaugbarkeitstest This “Aerospace Series“ Prestandard has been drawn up under the responsibility of ASD-STAN (Th
3、e Aerospace and Defense Industries Association of Europe - Standardization). It is published for the needs of the European Aerospace Industry. It has been technically approved by the experts of the concerned Domain following member comments. Subsequent to the publication of this Prestandard, the tec
4、hnical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and review by users and formal agreement of ASD-STAN, it will be submitted as a draft European Standard (prEN) to CEN (Europe
5、an Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN national members have then to implement the EN at national level by giving the EN the status of a national standard and by withdrawing any national standards conflicting with the EN. Edition
6、approved for publication 30 November 2005 Comments should be sent within six months after the date of publication to ASD-STAN Non-metallic Material Domain Copyright 2005 by ASD-STAN prEN 4195:2005 2 Contents Page Foreword2 1 Scope 3 2 Normative references 3 3 Principle3 4 Specimens and test apparatu
7、s.3 5 Test procedure.4 6 Analysis of hexavalent chromium4 7 Test report 4 8 Designation 5 Annex A (informative) 6 A.1 Diphenylcarbazide solution 6 A.2 Phosphoric-sulphuric acid .6 A.3 Preparation of standard chromium solutions.6 A.4 Calibration for diphenylcarbazide method6 Annex B (informative) Cal
8、culation of factor .8 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs Non-metallic Material Domain. After inquiries and votes carried out in accordance with the rules of ASD-STAN defined in ASD-STANs General Process Manual, this standard has received approval for
9、 Publication. prEN 4195:2005 3 1 Scope This standard defines a test procedure for the determination of the leaching rate of hexavalent chromium from the dry paint film of a chromate containing primer for aerospace use. The rate can be related to requirements either to prescribe the type of primer fo
10、r an intended use or for the purpose of batch quality consistency. The procedure is applicable to products intended for use in aerospace applications. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edit
11、ion cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3696, Water for analytical laboratory use Specification and test methods. EN 2090, Aerospace series Aluminium alloy AL-P2024- T3 Clad sheet and strip 0,3 mm a 6 mm. EN 233
12、4, Aerospace series Chromic-sulphuric acid pickle of aluminium and aluminium alloys. 3 Principle The test involves placing a dry film of chromate primer in distilled water in accordance with ISO 3696 for a period of time at a controlled temperature to allow soluble chromate to leach from the film in
13、to solution in the water. The water is collected for the measurement of dissolved hexavalent chromate by a suitable means. Because the rate of leaching can vary considerably over a period of time the collection time is divided into a number of periods of different duration appropriate to the rate of
14、 leaching over the collection period. Some of the water collected in the collection periods is not used for measurement because normally sufficient data is gained from other collections. Values of chromate leaching can be numerically expressed or for convenience plotted on a graph. 4 Specimens and t
15、est apparatus The apparatus shall consist of a stoppered test tube to hold the water and the painted test specimens. The test tube shall be maintained at a constant temperature, as specified, in a suitably controlled chamber. Test specimens shall be of aluminium alloy EN 2090. Test specimens shall b
16、e prepared by chrome sulphuric acid pickling in accordance with EN 2334 or other non chromate leaching pretreatment as may be specified in the relevant material specification. They shall then be sprayed with primer within four hours to give the paint thickness prescribed in the relevant material spe
17、cification. When dried and preconditioned as prescribed in the relevant material specification an area of 40 cm2shall be cut from the panel for leaching test immersion. All edges shall be uncoated. Using a test tube for the immersion, it is convenient to cut two panels of dimensions (10 2) cm. This
18、assumes that the panels are coated on one side only and are then placed back to back in the test tube. prEN 4195:20054 5 Test procedure A test specimen, prepared as above, shall be totally immersed in a stoppered tube containing 50 ml of distilled water maintained at a temperature of (40 2) C. The d
19、istilled water shall be renewed after 1, 2, 3, 4, 7, 10, 14, 18, 23, 29 and 36 days. The samples collected at the end of 2, 10 and 36 days only shall be analysed for chromate content as normally this is sufficient to determine the leach rate characteristics of the paint sample under test. However sa
20、mples from other collection periods can also be measured if additional data is required. At the end of the appropriate immersion time, the water in which the painted specimens have been immersed shall be poured into a 100 ml volumetric flask. The specimen and the test container shall be rinsed with
21、a volume of distilled water not exceeding 25 ml and this shall be added to the volumetric flask containing the first solution. Another 50 ml of distilled water shall be added to the original container to proceed with the test for the next immersion period. A suitable method of analysis for chromate
22、determination has been outlined in Annex A. Whether this or another method is employed for chromate concentration determination, the final volume of chromate containing solution, tube washings and reagents shall be 100 ml. The concentration of hexavalent chromium in the solution shall be measured an
23、d calculated as milligrams of chromate leached per square decimetre of paint film. 6 Analysis of hexavalent chromium A sample shall be taken from the 100 ml container and analysed for hexavalent chromium content. The result shall be determined as mg Cr per l and expressed as mg CrO4 per dm2of paint
24、film tested. NOTE For a 40 cm2exposed primer area this involves multiplying the quantity of hexavalent chromium in mg/l by a factor of 0,557 7. Details of the calculation of the factor for this case are given in Annex B. The quantity of CrO4 per dm2shall be converted into CrO4 per dm2per day leachin
25、g rate. This means that the value calculated for the test sample needs to be divided by the number of days over which the paint sample had been in contact with that sample of water since it had been previously renewed. Sample at 2 days duration 1-2 days divide by 1 Sample at 10 days duration 7-10 da
26、ys divide by 3 Sample at 36 days duration 29-36 days divide by 7 The results can be numerically expressed or for convenience can be plotted on a semi-logarithmic graph. 7 Test report The test report shall contain at least the following information: Complete identification of the paint used including
27、 suppliers code numbers, date of manufacture, batch number, material standard, etc. a) Reference to the test standard; b) The number of specimens tested; prEN 4195:2005 5 c) The paint thickness applied; d) Dimensions of specimen tested; e) The overall drying time between application and testing; f)
28、The method of analysis of chromate used for the determination; g) Date of test and traceability to individuals performing the test work; h) Any incident which may have affected the results and any deviation from the test method; i) Reference to the material standard; j) The test results. 8 Designati
29、on EXAMPLE Description block DETERMINATION OF CHROMATE LEACHING Identity block EN4195 Number of this standard prEN 4195:20056 Annex A (informative) The following is one of many methods used for determining chromate concentration in a solution. It uses a colormetric determination of diphenylcarbazide
30、 complex. A set of standard solutions are prepared with increasing chromium concentrations and are used to construct a suitable calibration curve. The concentration of chromium in the “unknown” solution can then be read off the graph. A.1 Diphenylcarbazide solution 40 g of phthalic anhydride shall b
31、e dissolved in 1 l of hot industrial ethyl alcohol The solution shall be cooled and 5 g of diphenylcarbazide added. This shall be stirred with a magnetic stirrer to dissolve. A.2 Phosphoric-sulphuric acid 375 ml of concentrated sulphuric acid (S.G. = 1,84) and 375 ml of concentrated phosphoric acid
32、(S.G. = 1,83) shall be added to 1 l of distilled water. A.3 Preparation of standard chromium solutions 2,828 g of dried “Analar” potassium dichromate shall be accurately weighed, dissolved in about 100 ml of distilled water and diluted to 1 l in a volumetric flask. This solution shall now contain 1
33、g/l (or 1 000 g/ml) of chromium. In order to obtain a solution containing 5 g/ml of chromium, 5 ml of the 1 g/l solution shall be pipetted into a 1 l volumetric flask and made up to the mark with distilled water. In obtain a solution containing 100 g/ml of chromium, 50 ml of the 1 g/l solution shall
34、 be pipetted into a 500 ml volumetric flask and made up to the mark with distilled water. NOTE Standard solutions prepared in this way are stable when stored in closed glass containers for a maximum of 12 months. A.4 Calibration for diphenylcarbazide method Using a burette, 2, 5, 10, 15 and 20 ml of
35、 5 g/ml standard solution shall be put into respective volumetric flasks. NOTE This is equivalent to 10, 25, 50, 75 and 100 g of chromium for calibration. 50 ml of distilled water shall be added to another 100 ml volumetric flask. This shall be used as a blank. The volume of solution in each flask s
36、hall be made up to approximately 50 ml with distilled water. 10 ml of the phosphoric/sulphuric acid solution and 10 ml of diphenylcarbazide shall be added. prEN 4195:2005 7 The solutions shall be made up to the mark with distilled water, thoroughly mixed and allowed to stand for 10 minutes. The stan
37、dards shall be poured into 1 cm cells, the optical density values shall be measured using the blanks a reference on a suitable spectrophotometer set at a wavelength of 540 nm. A graph of optical density versus chromium content of standards shall be plotted. For test samples the steps outlined in cla
38、uses 3 to 5 of this section shall be followed and the chromium content equivalent to the measured optical density shall be read from the calibration graph. NOTE A fresh graph must be produced daily or with each batch of samples. prEN 4195:2005 8 Annex B (informative) Calculation of factor The result
39、 shall be determined as mg Cr per l and expressed as mg CrO4 per dm2of paint film tested. NOTE For a 40 cm2exposed primer area this involves multiplying the quantity of hexavalent chromium in mg/l by a factor of 0,557 7. Mol wt of CrO4a 115,994 8 Atomic wt of Cr b 51,996 mg Cr per l Y mg Cr per 100 mls Y/10 mg CrO4per 100 mls Y*a/b/10 0,223 084 For 40 cm2Y*a/b/10 0,223 084 For 1 cm2Y*a/b/10/40 0,005 577 For 100 cm2 = 1 dm2Y*a/b/10/40*100 0,557 7
