1、AECMA PRENa2334 95 U LOL23Ll 08LOO 562 for publication 1995-1 2-29 AECMA STANDARD NORME AECMA AECMA NORM I - can be supplied by B.N.A.E. - Technopolis 54 - 199, rue Jean-Jacques Rousseau 92138 ISSY - LES - MOULINEAUX CEDEX - FRANCE prEN 2334 Edition 1 December 1995 PUBLISHED BY THE EUROPEAN ASSOCIAT
2、ION OF AEROSPACE INDUSTRIES (AECMA) Gulledelle 94 - B-1200 BRUXELLES - Tel. (32) 2 775 81 10 - Fax. (32) 2 775 81 11 ICs : 49.040.40 Descriptors : Aircraft industry, aluminium, aluminium alloys, cleaning ENGLISH VERSION Aerospace series Chromic-sulphuric acid pickle of aluminium and aluminium alloys
3、 Srie arospatiale Luft- und Raumfahrt Dcapage sulfochromique de laluminium et des alliages daluminium Beizen von Aluminium und Aluminiumlegierungen in Chromschwefelsure This “Aerospace series“ Standard has been drawn up under the responsibility of AECMA (The European Association of Aerospace Industr
4、ies). It is published on yellow paper in three equivalent versions (English, French, German). It will be submitted as a draft European Standard to CEN (European Committee for Standardization) for formal vote. I Edition aDDrOVed I The eauivalent versions in French and German languages 1 I I aecma 199
5、5 Page 3 prEN 2334 : 1995 1 Scope This standard specifies the acid chromate pickling of aluminium and aluminium alloys except those with a silicon content in excess of 2 % or a copper content in excess of 5 %. It is applicable whenever referenced. 2 Purpose of process 2.1 specimens used for qualific
6、ation and acceptance tests on adhesives, paints, sealants (treatment A). Reference surface treatment, e.g. prior to adhesive bonding or primer application to test 2.2 Final treatment for parts prior to adhesive bonding or primer application (treatment BI. 2.3 Pre-treatment before anodizing for adhes
7、ive bonding (treatment Cl. 2.4 - anodizing for other applications than adhesive bonding ; - other chemical treatments. Pre-treatment (treatment D) for : 3 Normative references This European Standard incorporates by dated or undated reference provisions from other publications. These normative refere
8、nces are cited at the 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 l
9、atest edition of the publication referred to applies. EN 2000 Aerospace series - Quality assurance EN aerospace products - Approval of the quality system of manufacturers 4 Information for the processor - Designation, see 13 ; - Number of the material standard and metallurgical condition of the latt
10、er ; - Sequence of operations ; - Areas to be processed ; - Treatment. 5 Condition of parts prior to processing Fabrication of the parts shall have been completed before pickling. - AECIA PRENs2334 95 1012311 0010102 987 = Process schedule Pre-treatments Pickling Post-treatments Page 4 EN 2334 : 199
11、5 Application, see treatment A B C D 7.1 7.2 7.2 7.2 8 8 8 8 9.1 9.1 9.1 9.1 9.2 9.2 9.3 9.3 6 Process schedule 7 Pre-treatments 7.1 7.1.1 hot alkaline solution. Cleaning for treatment A (see 2.1) Vapour degreasing, solvent cleaning or alkaline cleaning with a non-etching, non-silicated 7.1.2 Water
12、rinsing and check for water break, repeat cleaning if break occurs. 7.2 7.2.1 Cleaning for treatments B, C, D (see 2.2, 2.3 and 2.4) Heavily soiled parts shall be emulsion cleaned, vapour degreased or solvent cleaned. 7.2.2 If there is a natural oxide film, carry out abrasive blasting or chemical de
13、oxidizing. When pickling does not follow immediately after these operations, the parts shall be vapour degreased or cleaned with a hot alkaline solution. 7.2.3 solution. The alkaline solution shall be corrosion inhibited and preferably of a non-silicated type. For the parts to be bonded a non-silica
14、ted alkaline solution is mandatory. After alkaline cleaning, the parts shall be thoroughly water rinsed and inspected for water break. Cleaning shall be repeated if break occurs. If there is no significant natural oxide film, parts shall be cleaned with a hot alkaline 8 Treatment Immediately after f
15、inal cleaning, the parts shall be pickled in one of the solutions specified in annex A. To ensure a well pickled surface, the following shall be observed : - excessive bath loading and shielding of parts by each other shall be avoided ; - to ensure satisfactory adhesion and durability properties for
16、 treatments A and B or to obtain a satisfactory metal removal rate, pure aluminium and certain aluminium alloys with a very low - AECIA PRENm2334 75 LOL23LL OOLOL03 813 Page 5 prEN 2334 : 1995 copper content at the surface (clad aluminium alloys, AI-Mg alloys) require additional provisions. The part
17、s in these materials shall be either suspended on supporting jigs which shall be more noble (cathodic) relative to the materials to be treated, e.g. unclad AI-Cu alloy, or coupled to auxiliary cathodes. The position of the parts (anodes) relative to the cathodic areas and the cathodic to anodic area
18、 ratio shall be chosen carefully. Electrical contacts at several points shall be provided. 9 Post-treatments 9.1 Rinsing It shall be carried out as quickly as possible after pickling in running water with a temperature not exceeding 40 OC. The water used for final rinsing shall have a conductivity n
19、ot more than 70 pS/cm. 9.2 Drying The parts shall be dried except for those submitted for subsequent chemical or anodic treatment. The temperature shall not exceed 65 OC. The dry parts shall be protected againts contamination. 9.3 Treatment after drying As the adhesives and primers shall be applied
20、within 16 h of drying for treatment B and within 4 h for treatment A, necessary measures shall be taken. Moreover, it shall be ensured that the treated parts are stored under clean, dry conditions. 10 Required characteristics and inspection 10.1 Parts 1 O. 1 .1 Cleanliness No water break shall be ob
21、served when the surface is wetted with clean water (maximum temperature 35 OC) by immersion or spray. This operation has to be carried out after final rinsing. i O. 1.2 Appearance When subjected to visual inspection, the pickled surfaces shall be of a homogeneous appearance and free from pitting, st
22、ains and contamination. 10.2 Process 10.2.1 Air used for drying or other operations shall be substantially dry and free from oil. 10.2.2 Mercury or mercury compounds shall not be present in any of the materials used. 10.2.3 Chemical analyses of the pickling solutions shall be carried out at regular
23、intervals to determine the content of Cr6+, free acid, chloride, iron, copper, aluminium and, when requested, the Cr3+ content to ensure that the composition is maintained within the limits specified in annex A. - AECMA PRENb2334 95 LOL23Ll 0010104 75T D Page 6 EN 2334 : 1995 10.2.4 The purity of th
24、e rinsing water shall be determined by conductivity measurements. 10.2.5 carried out to ensure that the process has been correctly applied. When required for adhesive bonding, the test to the relevant bonding standard shall be I1 Quality assurance 1 1 .I See EN 2000. Approval of the processor 1 1.2
25、Process approval The processor shall carry out : - pickling on a series of test pieces or pre-production parts agreed between the purchaser and processor ; - tests specified in this standard, unless otherwise agreed between the purchaser and processor. When the test results have been accepted as sat
26、isfactory by the purchaser, he shall give his writtten approval to start production. The procedure shall not be changed without previous agreement from the purchaser. 11.3 Acceptance After pickling the parts shall have the required characteristics according to 10. The frequency and nature of the ins
27、pection shall be specified in the design documents or agreed between processor and purchaser. Parts not meeting the requirements shall be rejected. Parts which develop water break shall be reprocessed. 12 Health, safety and environmental aspects The locally applicable regulations and laws shall be o
28、bserved. 13 Designation EXAMPLE : EN2334A Treatment (see 2) I I AECMA PRENm2334 95 m 1012311 0010205 696 m Page 7 prEN 2334 : 1995 Annex A (normative) Table AI - Pickling solutions Pickling solutions Chromic acid (C,O3) Free sulphuric acid (H2SO4) Water 2) Chloride (as NaCI) Aluminium 3) Copper 3) I
29、ron Temperature Immersion time Sodium dichromate (Na2Cr207 . 2H20) Free sulphuric (H2SO4) Water 2) Chloride (as NaCI) Aluminium 3) Copper 3) Iron Temperature Immersion time Application to clause A and B 45 g/l to 55 g/l 220 g/l to 300 g/l Remainder 0,2 g/l max. 1,5 g/l min. 0,06 g/l to 1 g/l 1 g/l r
30、nax. 60 OC to 65 OC 28 min to 30 min 67 g/l to 83 g/l 220 g/l to 300 g/l Remainder 0,2 g/l max. 1,5 g/l min. 0,06 g/l to 1 g/l 1 g/l max. 60 OC to 65 OC 28 min to 30 min 1) 4) 5) 6) 4) 5) C and D 30 g/l to 55 g/l 150 g/l to 300 g/l Remainder 0,2 g/l max. 1 g/l max. 1 g/l rnax. 60 OC to 65 OC 1) - 4
31、20 min to 30 min 51 45 g/l to 83 g/l 150 g/l to 300 g/l Remainder 0,2 g/l max. 1 g/l max. 1 g/l max. 60 OC to 65 OC 20 min to 30 min 6) - 4) 51 1) H2SO4 : (4,5 to 5,5 x CrO3) 2) The solutions shall be prepared and maintained at the operating level with water having a conductivity not more than 100 p
32、S/cm and checked at regular intervals to ensure conformance with the tolerances specified for the composition. 3) To reach the required minimum aluminium and copper content, a fresh solution shall be either aged with AI-Cu unclad alloy chips or mixed with a part of an old pickling or anodizing solut
33、ion. As an alternative, copper sulphate may be added to reach the required minimum copper content. 4) The solution may be operated at 65 OC to 70 OC. In this case, the treatment time shall be 15 min to 25 min. 5) Parts machined all over which are not to be bonded, may be pickled for less than 20 min
34、. 6) H2SO4 : (2,5 to 3,5 x Na2Cr207 . 2H20) The solutions shall be discarded when pitting of parts occurs or when solid material starts to precipitate on cooling the solution to ambient temperature. The latter depends on the combined effect of dissolved metal and free acid content and can be expected at an aluminium content above 14 g/l.
