Etching alloy 4 paint

[trikerdrew]

:confused: Reading about paint lower down got me thinking!If etching alloy to paint it burns the surface,perhaps removing surface oxidization.Would painting/applying weak caustic soda have the same effect? :D

[Blackjack]

The active ingredient in etch primer is phosphoric acid I believe (least it used to be!). Caustic soda is an alkali so the answer is NO!!!!

Caustic soda also chews its way through aluminium quite badly, and really isn't a happy combination.

For relatively small pieces of ally, scotch brite wetted with a degreaser (white sprirt will do) to key the surface, followed immediately by wiping with a CLEAN rag soaked in the degreaser and then buffing dry with another clean rag and priming straight away can work fairly well. BUT in the event of the paint getting chipped or scatched the base metal will oxidise under the paint and lift it, which is what the etch primer really prevents.

If you ever break through the primer while flatting it, you basically have to start again, and you need to prime the part as soon as it is dried off from the last wipe over with degreaser. From there on the base metal should never be exposed to the air again for the best result. So get a good build of primer before you start flatting it.

Anodising is quite cheap and might work in place of an etch coat, seeing as it "seals" the surface of the ally.

[Suzukiron]

This is quite a common problem in the Aircraft Industry, infact its what i am currently dealing with....or will be when i go back to work tommorow!
The process that has been found to work, and is now employed on all comercial aircraft (or is currently being changed to...) is
Chromic Acid Anodise, Primer Coat, final coat.......the anodising and priming being carried out at the same time....
I got tonnes of litrature on this, but its boring as feck....unless yer concerned about paint peeling off yer wings!!
OK later days
Ron
:)

[Tom-madbiker]

try using a etch primer called prymol it is available from most model shops i have been using it for a few years and it works well :)