Aluminium oxide

VicS

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You dont say what you are painting but if possible the best solution is to remove all the oxide by grit blasting with a soft grit then etch prime.
 

Sans Bateau

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Thanks guys, it is a cast aluminium radar scanner bracket. A lot of the oxidization I have been able to remove with a wire wheel, but as you may expect some of the corrosion on the inside of the arms is proving difficult to get to.

On another thread someone mentioned Primcon as a primmer for aluminium, any views on that?
 

oldmonsty

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Clean off mechanically as best you can, clean down with warm soapy water, possibly lightly scrubbing, rinse and allow to dry and then you must use an etch primer
 
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Cymrogwyllt

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Aluninium oxidises in a matter of seconds after removing the oxide layer. It was a common demo for us. Clean the oxide layer off with acid to reveal shiny, silvery metal and watch the surface turn dull in a few seconds due to oxidation.
 

VicMallows

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I've tackled my cast aluminium hatch twice. The first time I took it down to bare metal as thoroughly as I could; etch primed;Blakes epoxy undercoats; Blakes epoxy top coats. Lasted about 5 years. The second time I thought 'this is a silly (expensive) lark' and simply gave it 3 coats of Hammerite smooth. (or probably the cheaper ScrewFix equivalent). Still good 10 years later.

Vic
 

Sans Bateau

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I've tackled my cast aluminium hatch twice. The first time I took it down to bare metal as thoroughly as I could; etch primed;Blakes epoxy undercoats; Blakes epoxy top coats. Lasted about 5 years. The second time I thought 'this is a silly (expensive) lark' and simply gave it 3 coats of Hammerite smooth. (or probably the cheaper ScrewFix equivalent). Still good 10 years later.

Vic

It cant be any worse than the original Scanstrut attempt at painting!
 

macd

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How do I neutralise aluminium oxide prior to repainting? I cant use Kurust, can I?

I suspect you're concerned about the furry white deposit on aluminium, which is not aluminium oxide. As cymrogwyllt writes, aluminium forms an oxide instantly in air. This oxide is stable and protective (much like chromium oxide protects stainless steel). Trouble is, in a salt/dissimilar metal environment, it just isn't protective enough.

There was a thread a day or so about Alocrom: www.ybw.com/forums/showthread.php?t=265005.
I've no experience of this stuff but it sounds interesting.
 

tross

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The last bit of research I did on this the Land Rover guys used phosphoric acid to clean prep the surface ( after removing the old paint) and then a etch primer.
 

Ubergeekian

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How do I neutralise aluminium oxide prior to repainting? I cant use Kurust, can I?

I was advised to use POR-15 Metal Ready when I dealt with some corrosion on my DS roof (which is aluminium). It seems to have worked fine - well, nothing has reappeared, five years on. It's available from Frost.

From the safety data sheet it's a mixture of Phosphoric Acid, Zinc Phosphate and Octylphenoxy Polyethanol Ethanol Triphenol Methane
 
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