1、BRITISH STANDARD AEROSPACE SERIES Chromate conversion coatings (yellow) for aluminium and aluminium alloys The European Standard EN 2437:2001 has the status ofa British Standard ICs 49.040 BS EN 2437:2002 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 2437:2002 Amd. No.
2、 National foreword Date Comments This British Standard, having been prepared under the direction of the Engineering Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 4 January 2002 This British Standard is the official English l
3、anguage version ofEN 2437:2001. The UKparticipation in its preparation was entrusted to Technical Committee ACE/44, Protective treatments and aircraft finishes, which has the responsibility to: - - aid enquirers to understand the text; present to the responsible European committee any enquiries on t
4、he interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. - A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Sta
5、ndards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Stand
6、ard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover,
7、an inside front cover, the EN title page, pages 2 to 9 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. O BSI 4 January 2002 ISBN O 580 37995 7 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 2437 December 2001 ICs 49.040 English v
8、ersion Aerospace series - Chromate conversion coatings (yellow) for aluminium and aluminium alloys Srie arospatiale - Chromatation jaune de laluminium et des alliages daluminium Luft- und Raumfahrt - Gelbchromatieren von Aluminium und Aluminiumlegierungen This European Standard was approved by CEN o
9、n 2 May 2001 CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be o
10、btained on application to the Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Management
11、Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPE
12、AN COMMITTEE FOR STANDARDIZATION EUROPISCHES KOMITEE FR NORMUNG COMIT EUROPEN DE NORMALISATION Management Centre: rue de Stassart, 36 B-1050 Brussels O 2001 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 2437:2001 E EN 2437:2001 (
13、E) Foreword This European Standard has been prepared by the European Association of Aerospace Manufacturers (AECMA) . After inquiries and votes carried out in accordance with the rules of this Association, this Standard has received the approval of the National Associations and the Official Services
14、 of the member countries of AECMA, prior to its presentation to CEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2002, and conflicting national standards shall be withdrawn at the latest
15、by June 2002. According to the CENKENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands
16、, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. 2 EN 2437:2001 (E) 1 Scope This standard specifies yellow chromate conversion coating of aluminium and aluminium alloys. It shall be applicable wherever referenced. 2 Purpose of process To increase corrosion resistance and to imp
17、rove the adhesion of paints and varnishes. Type B coatings are also suitable for the repair of mechanically damaged anodic coatings. 3 Normative references This European Standard incorporates by dated or undated reference provisions from other publications. These normative references are cited at th
18、e appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
19、 publication referred to applies. IS0 8081 Aerospace process - Chemical conversion coating for aluminium alloys - General purpose IS0 9227 Corrosion tests in artificial atmospheres - Salt spray tests EN 2000 Aerospace series - Quality assurance - EN aerospace products - Approval of the quality syste
20、m of manufacturers EN 2334 Aerospace series - Acid chromate pickling of aluminium and aluminium alloys 1) EN 3997 Aerospace series - Aluminium alloy AL-P2024- - T3 - Sheet and strip - 0,4 mm 0,42 g/m2 to 1,2 g/m2 for good corrosion protection, with or without painting. 1) Published as AECMA Standard
21、 at the date of publication of this standard 2) Published as AECMA Prestandard at the date of publication of this standard 3 EN 2437:2001 (E) 5.2 Materials - Category 1 : Aluminium alloy with an Si-content 33 %. 6 Information for the processor - Designation, see 16. - Areas not to be chromated. 7 Co
22、ndition of parts prior to processing Soldering, welding, mechanical operations and heat treatments (except for cold storage) shall be completed. The parts to be chromate coated after assembly (e.g. by spot welding) shall be pickled prior to assembly. Areas not to be chromate coated shall be suitably
23、 masked. 8 Pre-treatment 8.1 Cleaning The cleaning method shall be chosen according to the degree of contamination of the materials to be treated. In general, the most effective method is degreasing with solvents followed by cleaning in an alkaline solution (see annex A, A.2). 8.2 Rinsing The parts
24、shall be rinsed thoroughly, e.g. by immersion followed by spray washing. It is recommended that a further rinsing be carried out in deionised water with a maximum specific conductivity of 100 pS . cm-?. 8.3 Pickling It shall not cause pitting or any alterations to the metallurgical characteristics o
25、r mechanical strength of the material. The dimensions and the surfaces roughness value indicated on the drawings shall be observed. Pickling is normally carried out in a solution containing chromate. Other methods may be used (see annex A, A.4). 8.4 Rinsing See 8.2. 4 EN 2437:2001 (E) 9 Treatment Th
26、e parts are submerged in a still or agitated bath or treated by spraying or by brushpainting. An exemple of the possible composition of the chromate solution is given in annex A, A.5. However, a commercial product is generally used according to the manufacturers instructions. 10 Post-treatment 10.1
27、Rinsing See 8.2. The quality of the water shall not adversely affect the adhesion of paints or varnishes. Rinsing in hot water at 50 “C to 60 “C helps the drying process though the parts shall not be submerged for longer than 1 min. 10.2 Drying Drying may be carried out at ambient temperature using
28、dry, oil-free compressed air or hot air, at max. 60 “C. Alternative drying processes are permissible, provided that they do not have an adverse effect on the quality of the chromate coating and subsequent treatments. 10.3 Paints or varnishes The primer or the varnish coat shall be applied as soon as
29、 possible (max. 48 h after chromate coating) 11 Removal of the chromate coating Either by using a nitric acid solution (e.g. d = 1,4) at ambient temperature or a chromic acid solution (e.g. 40 g/l to 60 g/I) at 40 “C or mechanically by light abrasion. Strong alkaline pickling shall be avoided. 12 Re
30、quirements 12.1 Appearance The chromate coating shall be iridescent and range in colour from light yellow to dark yellow depending on the type of alloy. It shall be uniform and free from defects. Powdery coatings are not acceptable. Differences in colour due to different surface textures are permiss
31、ible. 12.2 Mass of coating See 5. 5 EN 2437:2001 (E) 12.3 Corrosion resistance After testing, a maximum of five corroding points is permissible per test piece and the diameter of each point shall not exceed 0,8 mm. The inspection shall not be carried out at less than 6 mm from: - the test piece edge
32、s; - the marking; - the mounting points. 13 Inspection and test methods 13.1 Parts Each batch shall be subjected to a visual inspection with the naked eye. The number of parts to be tested per batch shall be agreed between the purchaser and processor. For pipes, the inspection shall be carried out u
33、sing either an endoscope, or a cross section at a position where the geometry is the least favorable. 13.2 Test pieces The quality of the chromate coating shall be checked regularly and at least once every three months on at least three test pieces: - in aluminium alloy EN 3997 unplated; - dimension
34、s: 75 mm x 250 mm x 0,8 mm to 1 mm. 13.2.1 Mass per unit area See IS0 8081. 13.2.2 Corrosion resistance Chromate coated test pieces shall be: - aged for at least 24 h at ambient temperature; - exposed to a continuous salt spray test according to IS0 9227 at an angle of inclination of 6“ to the perpe
35、ndicular line: - thickness type A: 72 h; - thickness type B: 168 h; - rinsed in cold, running water, to remove sodium chloride residues; - air dried. Inspection shall be made visually. 13.3 Baths The solution shall be checked daily, prior to use, for liquid level, cleanness and temperature. Chemical
36、 analyses shall be carried out on the constitution of the bath and at regular intervals during operation. A fresh preparation is required if corrections remain ineffective. 6 EN 2437:2001 (E) Number of this standard Type (see 5.1) TT- Category (voir 5.2) 14 Quality assurance 14.1 Approval of the pro
37、cessor See EN 2000. 14.2 The processor shall carry out: Process a p prova I - chromate coating on a series of pre-production parts made up of the first batch of the parts; - tests specified in this standard, unless otherwise agreed between the purchaser and processor. When the test results have been
38、 accepted as satisfactory by the purchaser, he shall give his written approval to start production. The procedure shall not be changed without previous agreement from the purchaser. 14.3 Acceptance The frequency and nature of the inspection of parts and test pieces shall be defined in the definition
39、 documents or determined by agreement between the purchaser and processor. The parts showing defects on visual inspection shall be removed. Faulty areas can only be touched up with the purchasers agreement. 15 Health, safety and environmental aspects Locally applicable regulations and laws shall be
40、observed. 16 Designation EXAMPLE: Identity block 7 EN 2437:2001 (E) Annex A (normative) Recommend at on s for su dace preparation A.l Scope This annex describes solvents and bath preparation as well as processes for cleaning, pickling and yellow chromate conversion coating of aluminium and aluminium
41、 alloys. All processes providing results which are at least equivalent to the one described may also be applied. A.2 Degreasing A.2.1 In organic solvents This process comprises hot or cold degreasing at liquid or vapour state with authorized products. A.2.2 Alkaline cleaning This process may be used
42、 either alone or in addition to degreasing with solvents. Inhibitors shall be added to the degreasing baths in order to prevent the metal surfaces from being attacked. They can be used in a hot or cold state and with or without electric current. A.3 Cleaning by abrasive blasting A.3.1 Coarse cleanin
43、g This type of cleaning is achieved by means of blasting with a grain size 100 pm, with or without water. This process is not applicable to thin parts or parts with low surface roughness. A.3.2 Fine cleaning This type of cleaning is achieved by blasting with a grain size 100 pm, with or without wate
44、r. After cleaning remove any blasting medium still adhering to the parts and decontaminate the parts by suitable pickling. 8 EN 2437:2001 (E) A.4 Pickling A.4.1 Acid pickling A.4.1 .I Acid chromate pickling for class 1 materials See EN 2334 A.4.1.2 Other acid pickling media for materials of classes
45、1 and 2 Commercial or other products, e.g. those containing fluorides, may be used. A.4.2 This process, based on sodium hydroxide shall not be used for parts with close tolerances or for parts fastened by rivets or spot welding. Moreover, it increases surface roughness. The degreased metal is immers
46、ed in the following solution: Alkaline pickling for class 1 materials - Sodium hydroxide : 26gto50g; - Sodium heptonate or gluconate : 0,75 g to 1 ,O g; - Temperature : 40 OC to 65 OC. The reaction is very strong and normally an immersion time of 15 s to 1 min is sufficient. The rate of removal by t
47、he alkaline bath is 0,6 pmlmin to 13 pmlmin. A.4.3 De-smutting The film remaining after akaline pickling and some acid-pickling processes shall be removed by immersion in a solution of 30 % to 50 % by volume of nitric acid (d = 1,4) at ambient temprature. A.5 Chromate coating The following preparati
48、on may be used as the bath solution: - Na2Cr207. 2H20 - NaF - K3 Fe (CN)6I - Water - PH - Solution temperature - Treatment time - “03 73 gll; 1 gll; 5 gll; 1,15 gll; maximum specific conductivity 100 pS . cm-; 1,2 to 2,2; 15 OC to 55 OC; 5 s to 8 min. 9 BS EN 243 7:2002 BSI 389 Chiswick High Road Lo
49、n don w4 4AL BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Re vi si ons British Standards are updated by amendment or revision. Users of British Standards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretar
