ASD-STAN PREN 4707-2012 Aerospace series Acid pickling of aluminum and aluminum alloy without hexavalent chromium (Edition P 1).pdf

1、ASD-STAN STANDARD NORME ASD-STAN ASD-STAN NORM prEN 4707 Edition P 1 May 2012 PUBLISHED BY THE AEROSPACE AND DEFENCE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATIONAvenue de Tervuren, 270 - B-1150 Brussels - Tel. + 32 2 775 8126 - Fax. + 32 2 775 8131 - www.asd-stan.orgICS: Descriptors: ENGLISH V

2、ERSION Aerospace series Acid pickling of aluminum and aluminum alloy without hexavalent chromium Srie arospatiale Dcapage acide de laluminium et des alliages daluminium sans chrome hexavalent Luft- und Raumfahrt Acid Beizen von Aluminium und Aluminiumlegierungen sechswertiges Chrom-frei This “Aerosp

3、ace Series“ Prestandard has been drawn up under the responsibility of ASD-STAN (The AeroSpace and Defence 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 fol

4、lowing member comments. Subsequent to the publication of this Prestandard, the technical 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

5、 ASD-STAN, it will be submitted as a draft European Standard (prEN) to CEN (European 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 st

6、andard and by withdrawing any national standards conflicting with the EN. Edition approved for publication 01 Mayl 2012 Comments should be sent within six months after the date of publication to ASD-STAN Metallic Material Domain Copyright 2012 by ASD-STAN prEN 4707:2012 (E) 2 Contents Page Foreword

7、2 1 Scope 3 2 Purpose of process .3 3 Normative references 3 4 Information for the processor 3 5 Condition of parts prior to processing 4 6 Process schedule 4 7 Pre-treatments 5 8 Treatment 5 9 Rinsing 6 10 Drying 6 11 Required characteristics and inspection 6 12 Quality assurance 7 13 Health, safet

8、y and environmental aspects 7 Annex A (normative) Pickling bath 8 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs Metallic Material Domain. After inquiries and votes carried out in accordance with the rules of ASD-STAN defined in ASD-STANs General Process Manual,

9、 this standard has received approval for Publication. prEN 4707:2012 (E) 3 1 Scope This standard specifies the acid pickling of aluminium and aluminium alloys. It is applicable whenever referenced. 2 Purpose of process 2.1 Pre-treatment before penetrant testing/penetrant inspection. 2.2 Pre-treatmen

10、t before anodizing. 2.3 Final treatment for parts prior to adhesive bonding application. 2.4 Final treatment before welding or brazing. 2.5 Pre-treatment before chemical milling. 2.6 Final treatment for parts prior to painting application. 2.7 Pre-treatment for parts prior to surface conversion coat

11、ings. 2.8 Desmutting (Blanchiment), after alkaline etching or acid pickling. 3 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the refer

12、enced document (including any amendments) applies. EN 9100, Quality Management Systems Requirements for Aviation, Space and Defence Organizations 4 Information for the processor Designation; Number of the material standard and metallurgical condition of the latter; Sequence of operations; Areas to b

13、e processed; Treatment. prEN 4707:2012 (E) 4 5 Condition of parts prior to processing Fabrication of the parts shall have been completed before pickling. Toolings: Toolings, fixturings, and metal tooling masking must be protected from the corrosion and/or free from corrosion or another deterioration

14、 prejudicial 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 treatment

15、 between parts and tank equipments, and between various parts. Tanks and rackings: Materials used must be resistant to temperature and chemically compatible with the products involved in the sequence of operations. 6 Process schedule The pickling process shall be performed according to Table 1. Tabl

16、e 1 Process schedule Post Pickling processes Penetrant testing/ penetrant inspection Anodizing Adhesive bonding application Welding or brazing Preparation before masking for chemical milling Painting application Surface conversion coatings Desmutting, after etching or pickling Pre-treatments Clause

17、7 Applicable Applicable Applicable Applicable Not applicable Applicable Applicable Applicable Pickling Clause 8 Applicable Applicable Applicable Applicable Applicable Applicable Applicable Applicable Post-treatments Rinsing Applicable Applicable Applicable Applicable Applicable Applicable Applicable

18、 Applicable Drying Applicable Not applicable Applicable Applicable Applicable Applicable Not applicable Not applicable Post pickling maximum lead-time 16 h aImmediately in process 8 h 8 ha 8 h a or Immediatelyin process 16 h aImmediately in process Immediatelyin process aRecommended (in case of over

19、 lead time an appropriate storage and visual inspection (according 12.1.2) should be carried out before and after the post pickling process). prEN 4707:2012 (E) 5 7 Pre-treatments Heavily soiled/Polluted parts shall be emulsion cleaned, vapour degreased or solvent cleaned. If there is a significant

20、natural oxide film (ex.: 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 solvent. NOTE If necessary (laminated parts / oxidized parts), do a chemical deoxidiz

21、ing (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; preferably of a non-silicated type (especially for dye penetrant inspection). Generally alkalin

22、e solutions with pH between 9 and 11 are considered as a degreasing-etching solutions, whereas those with pH between 7 and 9, are considered only as a degreasing solution. For the parts to be bonded, a non-silicated alkaline solution is mandatory. 3) After alkaline degreasing/cleaning, the parts sha

23、ll be thoroughly water rinsed and inspected for water break. Cleaning shall be repeated if break occurs. 8 Treatment Immediately after pre-treatments, the parts shall be pickled in one of the solutions specified below. To ensure a well pickled surface, excessive bath loading and shielding of parts b

24、y each other shall be avoided: Type of substances that can be used in pickling: Nitric or sulfonitric; Phosphosulfonitric; Sulfonitro-ferric fluoride free; Sulfonitro-ferric with fluoride. prEN 4707:2012 (E) 6 9 Rinsing After each treatment bath, water rinsing is mandatory. This operation has to be

25、composed by at least one recycled rinsing. Recycled rinsing is generally completed by non-recycled or low-flow rate rinsing. Several quality of rinsing water can be used but the water used before surface treatment (see Table 1) rinsing shall have a conductivity not more than 70 S/cm. Rinsing shall b

26、e carried out consecutively to the pickling step in running water with a temperature not exceeding 40 C. 10 Drying The parts shall be dried except for those submitted for subsequent chemical treatment, anodic treatment or desmutting/chemical conversion The temperature shall not exceed 80 C. After dr

27、ying, parts shall be protected against contamination. In case of bonding and paint applications, parts shall be stored under clean, dry conditions. 11 Required characteristics and inspection 11.1 Parts 11.1.1 Inspection before treatment By visual inspection, make sure that the parts to be protected/

28、treated are free from defects such as: scratches, corrosion pits, cracks prejudicial to the aspect or the effectiveness of protection. Adherent chips and metal particles must be removed beforehand using a clean cloth. 11.1.2 Cleanliness During the degreasing phases, each rinsing operation must be fo

29、llowed by a water break test in order to evaluate the wettability (and 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 without any discontinuity in the film. Otherwise, degreasing phases have

30、 to be repeated. 11.1.3 Inspection after treatment When subjected to visual inspection, the pickled surfaces shall be of a homogeneous appearance and free from pitting, stains and contamination. 11.2 Process 11.2.1 Air used for drying or other operations shall be substantially dry and free from oil.

31、 11.2.2 Chemical analysis of the pickling solutions (and different baths involved in the sequence of operations) shall be carried out at regular intervals to determine the content of heavy metal, chloride, iron copper etc., when requested. prEN 4707:2012 (E) 7 11.2.3 The bath shall be discarded when

32、 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 polluant contents. 11.2.4 The purity of the rinsing water shall be determined by conductivity/re

33、sistivity measurements. 11.2.5 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. 11.2.6 Each pickling process must be characterized by its specific etching rate range. All pickling process must no

34、t lead to localized attack. 11.2.7 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 specified according to final customer requirements

35、. 12 Quality assurance 12.1 Approval of the processor See EN 9100. 12.2 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 the purcha

36、ser and processor (e.g.: dissolution rate, morphology, roughness, ). 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 purchaser. 12.3 Ac

37、ceptance After pickling the parts shall have the required characteristics according to Clause 12. 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 which de

38、velop water break shall be reprocessed. 13 Health, safety and environmental aspects The locally applicable regulations and laws shall be observed. prEN 4707:2012 (E) 8 Annex A (normative) Pickling bath Table A.1 Pickling bath Post pickling application Penetrant testing/ Penetrant inspection Anodizin

39、g Adhesive bonding application Chemical milling Welding or brazing Painting/ Organic film application Surface conversion coatings Desmutting, after etching or pickling Nitric or sulfonitric Applicable Applicable Applicable Applicable Applicable Applicable Applicable Applicable Phospho-sulfonic Not a

40、pplicable Applicable Not applicable Not applicable Not applicable Applicable Applicable Not applicable Sulfonitro-ferric without fluoride Applicable Applicable Applicable Applicable Applicable Applicable Not applicable Applicable Sulfonitro-ferric with fluoride Applicable Applicable Not applicable Applicable Applicable Applicable Not applicable Applicable