| Chromic
Acid Anodising
Chromic acid anodising is a specialist surface finish used
primarily within the defence and aerospace sectors and industries
where subsequent painting/adhesive bonding is required or
in applications where crack detection is sought. Chromic acid
anodising is the preferred process for the treatment of castings
and other components where the minimisation of the loss of
fatigue strength resulting from the anodising process is desirable.
Restrictions
-
This process is not suitable for use on aluminium
alloys containing a specified maximum total of 7%
copper, nickel and iron or more than 6% copper.
-
Chromic
acid anodising is not suitable for colour dyeing due
to the thin (2-3µm) coating layer as most colours
will appear blotchy, however black dyeing is usually
quite reliable and effective.
-
The
chromic acid anodising process is not suitable for
welded assemblies or components with blind holes.
Painting
- Adhesive Bonding
For customers that require components painted, or used in
composite structures, we offer an overnight service with guaranteed
availability at an agreed time the next morning, allowing
you time to transport your items for finishing or manufacture
before the anodised coating cures, usually within 8-16 hours.
Maximum
Size Criteria
The table below outlines the maximum size criteria for chromic
acid anodising:
Dimension |
Clear |
Black |
Length |
2430mm
(8') |
1829mm
(6') |
Width |
910mm
(3') |
910mm
(3') |
Depth |
910mm
(3') |
910mm
(3') |
Coating
Thickness
Chromic acid anodising results in a thin 2-3µm coating.
Available
Standards
We predominantly work to 2 specific standards as detailed
below although we are happy to work to any specification provided.
- DEF
STAN 03-24 (formerly DEF 151 Type 2)
- BS1615
- US
MIL-A-8625 Type 1
Sealing
& Dyeing
Two seals are available for application after chromic acid
anodising:
- Colour
dyeing prior to sealing - black
- Hot
De-mineralised Water Seal
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