coyoteboy
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| posted on 15/6/12 at 11:26 AM |
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Cleaning alloy engines/boxes of oxide
So after about 10 hours of scrubbing with acids and alkalis of various strengths I managed to get my block back to what looked like a nice surface
with the odd bit of corrosion. Rinsed it all off with clean water for ages, dried and painted it with matte black enamel paint. Oxides show/grow
through. Any ideas? I could use a nice thick gloss paint and cover it all but a) I don't want a gloss block and b) it'll carry on
underneath.
Anyone found a way of properly getting rid of alu oxides without mechanical removal? I can't physically scrape all of it off due to the casting
shapes.
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imp paul
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| posted on 15/6/12 at 12:12 PM |
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dry ice soda blast is the way to do it and it looks really good
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loggyboy
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| posted on 15/6/12 at 12:25 PM |
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http://www.youtube.com/watch?v=YI_Bnl6l-OY
Mistral Motorsport
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coyoteboy
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| posted on 15/6/12 at 01:24 PM |
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I have a grit blaster but it isn't helpful in this case as it is built up. Soda or dry ice is nice but don't know anyone around who will
do it and transporting the parts isn't going to happen!
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loggyboy
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| posted on 15/6/12 at 01:37 PM |
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DIY soda blasting as in the link!
Mistral Motorsport
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coyoteboy
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| posted on 15/6/12 at 01:43 PM |
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This is what I have so far!
 
Description
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Confused but excited.
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| posted on 15/6/12 at 06:29 PM |
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Probably a silly question but did you use an etch primer before painting it black?
Tell them about the bent treacle edges!
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coyoteboy
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| posted on 15/6/12 at 07:30 PM |
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No, because the etch primer i would find was deigned for steel and the paint i used claimed it could be painted directly onto metal after a
cleaning.
[Edited on 15/6/12 by coyoteboy]
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blakep82
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| posted on 15/6/12 at 07:59 PM |
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now, i'm no expert, and this could be wrong, but acids are oxidising agents, so perhaps the acids you've used are causing a reaction
later? a stainless steel wire brush would be better i'd have thought?
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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coyoteboy
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| posted on 15/6/12 at 08:16 PM |
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Indeed, this iswhere my problems stem from I think. All the advice I could find said to use acid to remove it a per alloy wheel cleaners. It
didn't help and instead I tried concentrated sodium hydroxide which is used to remove anodising (Al oxide) but that didn't help either. So
I rinsed it all off for ages.with clean water. The NaOH cleaned off the surface stuff but didn't touch the heavy stuff. Tried a wire brush but
can only get to larger surfaces and it's the tight stuff that is worst corroded.
[Edited on 15/6/12 by coyoteboy]
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coyoteboy
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| posted on 19/6/12 at 01:52 PM |
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I was hoping there'd be a few with experience on here  Looks like I'm a bit stuffed.
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paulf
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| posted on 20/6/12 at 10:37 PM |
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You need to do it with an etch primer suitable for aluminium, the chemicals that you cleaned it with would have removed the original oxide layer but
it re oxidises almost immediately when exposed to air. The etch primer has an acid component that eats into the alloy and then the paint keys straight
to it before it can oxidise.
I had a cam cover soda blasted and then painted it with engine enamel and found that it had started to flake after a few months due to no primer, the
alloy panels on my car have been no problem as I used an etch primer .
Paul
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RichG
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| posted on 21/6/12 at 06:12 AM |
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AUTOTEK PROFESSIONAL GREY ACID ETCH PRIMER – ALUMINIUM, GALVANISED METAL PRIMER | eBay
This should do the trick
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coyoteboy
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| posted on 21/6/12 at 08:24 AM |
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Cheers folks, much appreciated. I'll grab some alu etch primer and see how I get on with the heads and sump areas. I'm not sure where
I'll go with the bit I've painted as I can't strip it very easily now. What a pain.
Thanks again
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