BS EN 4707:2014 pdf download.Aerospace series — Acid pickling of aluminium and aluminium alloys without hexavalent chromium.
BS EN 4707 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-treatment 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 coatings.
2.8 Desmutting (Blanchiment), after alkaline etching or acid pickling.
4 Information for the processor
— Designation;
— Number of the material standard and metallurgical condition of the latter;
— 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.
Toolings:
Toolings, fixturings, and metal tooling masking must be protected from the corrosion and/or free from corrosion or another deterioration prejudicial to the treatment during their use.
Design of the toolings and racking must be achieved in order to:
7 Predreatments
Heavily soiled/Polluted parts shall be emulsion cleaned, vapour ciegreased or solvent cleaned.
If there is a significant 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 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;
— preferably of a non-silicated type (especially for dye penetrant inspection).
Generally alkaline 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 shall be thoroughly water rinsed and inspected for water break. Cleaning shall be repeated if break occurs.BS EN 4707 pdf.