ASD-STAN PREN 4707-2018 Aerospace series Acid pickling of aluminium and aluminium alloys without hexavalent chromium (Edition P 2).pdf

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1、ASD-STAN STANDARD NORME ASD-STAN ASD-STAN NORM ASD-STAN prEN 4707 Edition P 2 March 2018 PUBLISHED BY THE AEROSPACE AND DEFENCE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATION Rue Montoyer 10 - 1000 Brussels - Tel. 32 2 775 8126 - Fax. 32 2 775 8131 - www.asd-stan.org ICS: 25.220.20; 49.025.20 Su

2、persedes edition P 1 of May 2012 and will supersede EN 4707:2014 Descriptors: Aircraft industry, aluminium, aluminium alloys, cleaning, etching, pickling ENGLISH VERSION Aerospace series Acid pickling of aluminium and aluminium alloys without hexavalent chromium Luft- und Raumfahrt Saures Beizen von

3、 Aluminium und Aluminiumlegierungen ohne hexavalentem Chrom Srie arospatiale Dcapage acide de laluminium et des alliages daluminium sans chrome hexavalent This “Aerospace Series“ Prestandard has been drawn up under the responsibility of ASD-STAN (The AeroSpace and Defence Industries Association of E

4、urope - 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 technical content shall not be changed to an extent th

5、at interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and review by users and formal agreement of ASD-STAN, the ASD-STAN prEN will be submitted as a draft European Standard (prEN) to CEN (European Committee for Standardization) fo

6、r 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. ASD-STAN Technical Committee approves that:

7、“This document is published by ASD-STAN for the needs of the European Aerospace Industry. The use of this standard is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” ASD-ST

8、AN reviews each standard and technical report at least every five years at which time it may be revised, reaffirmed, stabilized or cancelled. ASD-STAN invites you to send your written comments or any suggestions that may arise. All rights reserved. No parts of this publication may be reproduced, sto

9、red in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of ASD-STAN. Order details: E-mail: salesasd-stan.org Web address: http:/www.asd-stan.org/ Edition approved for publication 1st March

10、 2018 Comments should be sent within six months after the date of publication to ASD-STAN Material Domain Copyright 2018 ASD-STAN prEN 4707:2018 (E) 2 Contents Page Foreword 2 1 Scope 3 2 Normative references 3 3 Terms and definitions . 3 4 Purpose of process . 3 5 Information for the processor 3 6

11、Condition of parts prior to processing 3 7 Process requirements . 4 8 Required characteristics and inspection 6 9 Quality assurance 7 Annex A (normative) Pickling bath . 9 Annex B (informative) Example of composition and pickling parameters for pickling bath type C . 10 Annex C (informative) Standar

12、d evolution form 11 Bibliography 12 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs 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 fo

13、r Publication. prEN 4707:2018 (E) 3 1 Scope This standard specifies the acid pickling of aluminium and aluminium alloys free from hexavalent chromium. 2 Normative references There are no normative references in this document. 3 Terms and definitions No terms and definitions are listed in this docume

14、nt. ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at http:/www.electropedia.org/ ISO Online browsing platform: available at http:/www.iso.org/obp 4 Purpose of process 4.1 Pre-treatment before penetrant testing/penetra

15、nt inspection. 4.2 Pre-treatment before anodizing. 4.3 Final treatment for parts prior to adhesive bonding application. 4.4 Final treatment before welding or brazing. 4.5 Pre-treatment before chemical milling. 4.6 Final treatment for parts prior to painting application. 4.7 Pre-treatment for parts p

16、rior to surface conversion coatings. 4.8 Desmutting, after alkaline etching or acid pickling. 5 Information for the processor Designation, see 9.5; Number of the material standard and metallurgical condition of the latter; Sequence of operations; Areas to be processed; Treatment. 6 Condition of part

17、s prior to processing Fabrication of the parts shall have been completed before pickling. prEN 4707:2018 (E) 4 7 Process requirements 7.1 Process conditions 7.1.1 Toolings Toolings, fixturings, and metal tooling masking must be protected from the corrosion and/or free from corrosion or another deter

18、ioration detrimental to the treatment during their use. Design of the toolings and racking must be achieved in order to: avoid any retention of air or solution on the parts, allow the neutralisation and the suppression of the solutions during rinsing operations, avoid any accidental contact during t

19、reatment between parts and tank equipments, and between various parts. 7.1.2 Tanks and racks Materials used must be resistant to temperature and chemically compatible with the products involved in the sequence of operations. 7.2 Process schedule 7.2.1 General The pickling process shall be performed

20、according to Table 1. Table 1 Process schedule Post Pickling processes Penetrant testing/ penetrant inspection Anodizing Bonding Welding or brazing Preparation before masking for chemical milling Painting/ organic film application Surface conversion coatings Desmutting, after etching or pickling Pre

21、-treatments Subclause 7.2.2 Applicable Applicable Applicable Applicable Not applicable Applicable Applicable Applicable Pickling Subclause 7.2.3 Applicable Applicable Applicable Applicable Applicable Applicable Applicable Applicable Post-treatments Rinsing Subclause 7.2.4 Applicable Applicable Appli

22、cable Applicable Applicable Applicable Applicable Applicable Drying Subclause 7.2.5 Applicable Not applicable Applicable Applicable Applicable Applicable Not applicable Not applicable Post pickling maximum lead-time 16 h a Immediately in process 8 h 8 h a 8 h a or Immediately in process 16 h a Immed

23、iately in process Immediately in process a Recommended (in case of over lead time an appropriate storage and a visual inspection (according to 8.1.3) should be carried out before and after the post pickling process). prEN 4707:2018 (E) 5 7.2.2 Pre-treatments Heavily oiled contaminated parts shall be

24、 emulsion cleaned, vapour degreased or solvent cleaned. If there is a significant natural oxide film (e.g.: laminated parts or oxidized parts), carry out abrasive blasting or chemical deoxidizing. Sequence of operations 1) Pre-degreasing: alkaline degreasing (with rinsings); or solvent; or vapour so

25、lvent. NOTE If necessary (laminated parts/oxidized parts), carry out a chemical deoxidizing (with rinsings) or abrasive blasting after pre-degreasing. 2) A second alkaline degreasing shall be performed after pre-degreasing, if necessary. The alkaline degreasing shall be: corrosion inhibited; prefera

26、bly silicate free and borate free type (especially for dye penetrant inspection). Generally alkaline solutions with pH between 9 and 11 are considered as degreasing-etching solutions, whereas those with pH between 7 and 9, are considered only as degreasing solutions. For the parts to be bonded, a si

27、licated free alkaline solution is mandatory. 3) After alkaline degreasing/cleaning, the parts shall be thoroughly water rinsed and inspected for water break. Cleaning shall be repeated if break occurs. 7.2.3 Treatment Immediately after pre-treatments, the parts shall be pickled in one of the solutio

28、ns specified below. To ensure a well pickled surface, excessive bath loading and shielding of parts by each other shall be avoided: Type of substances that can be used in pickling: Type A: Nitric or sulfonitric; Type B: Phosphosulfonitric; Type C: Sulfonitro-ferric fluoride free; Type D: Sulfonitro-

29、ferric with fluoride. Table A.1 specifies pickling bath to be used depending on the application. prEN 4707:2018 (E) 6 7.2.4 Rinsing After each treatment bath, water rinsing is mandatory. This operation has to be composed by at least one recycled rinsing. Recycled rinsing is generally completed by no

30、n-recycled or low-flow rate rinsing. Several quality of rinsing water can be used for rinsing but the water used before surface treatment (see Table 1) shall have a conductivity not more than 20 S/cm. Rinsing shall be carried out consecutively to the pickling step in running water with a temperature

31、 not exceeding 40 C. 7.2.5 Drying The parts shall be dried except for those submitted for subsequent chemical treatment, anodizing or desmutting/chemical conversion. The temperature shall not exceed 80 C. After drying, parts shall be protected against contamination. In case of bonding and paint appl

32、ications, parts shall be stored under clean, dry conditions. 8 Required characteristics and inspection 8.1 Parts 8.1.1 Inspection before treatment By visual inspection, make sure that the parts to be protected/treated are free from defects such as: scratches, corrosion pits, cracks, etc. prejudicial

33、 to the appearance or the effectiveness of the protection. Adherent chips and metal particles must be removed beforehand using a clean cloth. 8.1.2 Cleanliness During the degreasing phases, each final rinsing operation must be followed by a water break test in order to evaluate the wettability (and

34、the cleanliness) of the surfaces. This test consists of covering the parts with a uniform water film. This water film must cover the parts for at least 30 s at ambient temperature without any discontinuity in the film. Otherwise, degreasing phases have to be repeated. This test is optional for autom

35、atic lines. 8.1.3 Inspection after treatment When subjected to visual inspection, the pickled surfaces shall be of a homogeneous appearance and free from pitting, stains and contamination. 8.2 Process 8.2.1 Air used for drying or other operations shall be substantially dry and free from oil. 8.2.2 C

36、hemical analysis of the pickling solutions (and of the different baths involved in the sequence of operations) shall be carried out at regular intervals to determine the content of active products, heavy metal (e.g. iron, copper), chloride, etc., when requested. prEN 4707:2018 (E) 7 8.2.3 The bath s

37、hall be discarded when pitting of parts occurs or when solid material starts to precipitate on cooling the solution to ambient temperature. The process must be managed by monitoring the significant parameters as aluminium and contaminant contents. 8.2.4 The purity of the rinsing water shall be deter

38、mined by conductivity/resistivity measurements. 8.2.5 When required for adhesive bonding, the test to the relevant bonding standard shall be carried out to ensure that the process has been correctly applied. 8.2.6 Each pickling process must be characterized by its specific etching rate range. All pi

39、ckling process must not lead to localized attack. 8.2.7 The etching rate of the complete sequence of operations must be periodically measured to ensure the control of the process. NOTE The etching rate and maximum dipping time cannot be generally specified but has to be compliant with final customer

40、 requirements. 9 Quality assurance 9.1 Approval of the processor See EN 9100. 9.2 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

41、the purchaser and processor (e.g.: dissolution rate, morphology, roughness, etc.). When the test results have been accepted/considered 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 purc

42、haser. 9.3 Acceptance After pickling the parts shall have the required characteristics according to 8.1. The frequency and nature of the inspection shall be specified in the design documents or agreed between processor and purchaser. Parts that do not meet the requirements shall be rejected. Parts w

43、hich develop water break shall be reprocessed. prEN 4707:2018 (E) 8 9.4 Health, safety and environmental aspects The locally applicable regulations and laws shall be observed. 9.5 Designation EXAMPLE EN4707 A Number of this standard Pickling bath type (see Subclause 7.2.3) prEN 4707:2018 (E) 9 Annex

44、 A (normative) Pickling bath Table A.1 Type Pickling bath Post pickling application Penetrant testing/ Penetrant inspection Anodizing Bonding Chemical milling Welding or brazing Painting/ Organic film application Surface conversion coatings Desmutting, after etching or pickling A Nitric or sulfonitr

45、ic Applicable Applicable Applicable Applicable Applicable Applicable Applicable Applicable B Phospho-sulfonitric Not applicable Applicable Not applicable Not applicable Not applicable Applicable Applicable Not applicable C Sulfonitro-ferric fluoride free Applicable Applicable Applicable Applicable A

46、pplicable Applicable Applicable Applicable D Sulfonitro-ferric with fluoride Applicable Applicable Not applicable Applicable Applicable Applicable Applicable Applicable prEN 4707:2018 (E) 10 Annex B (informative) Example of composition and pickling parameters for pickling bath type C Table B.1 Type

47、Pickling bath Composition Pickling parameters C Sulfonitro-ferric without fluoride Sulphuric acid (H2SO4) 275 g/l to 300 g/l Temperature 50 C to 60 C Nitric acid (HNO3) 120 g/l to 175 g/l Immersion time 8 minutes to 10 minutes Ferric ion (Fe3+) a 15 g/l to 20 g/l Water b Remainder Aluminium 15 g/l m

48、ax. Copper 1 g/l max. a Ferric iron can be added as ferric sulphate Fe2(SO4)3 or ferrous sulphate FeSO4. b The solutions shall be prepared and maintained at the operating level with water having a conductivity 20 S/cm and checked at regular intervals to ensure conformance with the tolerances specifi

49、ed for the composition. prEN 4707:2018 (E) 11 Annex C (informative) Standard evolution form The main changes with respect to the previous edition are listed in Table C.1. Table C.1 Main changes introduced prEN/EN number Edition Publication date Modifications prEN 4707 1 05/2012 - 2 04/2018 1 Scope: Add of “free from hexavalent chromium“. 2 - Normative references: EN 9100 is not a normative reference anymore. EN 9100 has b