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#4501227 - 08/29/17 11:44 AM Filling in pitted aluminium?
Mr_Accord Offline

Registered: 01/24/07
Posts: 446
Loc: LBP
Im attempting to refinish a set of old mirrors where the aluminium housings started to corrode with alu oxide and peel up the paint. I stripped the paint/wire brushed the surface clean, but there is small pitted bumps all over the surface. What is a good product to apply overtop to fill in the imperfections and can be sanded smooth to allow priming and painting? Bondo? Glazing putty? JB Weld? other?


Edited by Mr_Accord (08/29/17 11:45 AM)
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#4501231 - 08/29/17 11:49 AM Re: Filling in pitted aluminium? [Re: Mr_Accord]
Johnny2Bad Offline

Registered: 05/20/13
Posts: 1927
Loc: Saskatchewan, Canada
Glazing putty if the pits are not too big. If they are everywhere, a sandable high-solids primer.

What, exactly, is the reason the aluminum is corroding? There generally has to be some environmental issue to cause it. High sulphur in your local environment, maybe? Air pollution can cause metals to corrode prematurely. If that's the case, you may want to consider an epoxy primer.

Aluminum oxidizes almost instantly upon contact with air. The oxide protects the underlying metal from corrosion. So for some reason that isn't happening in your case, something is interacting with the oxide and allowing it to corrode.
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#4501248 - 08/29/17 12:27 PM Re: Filling in pitted aluminium? [Re: Johnny2Bad]
Mr_Accord Offline

Registered: 01/24/07
Posts: 446
Loc: LBP
Not sure. Its a common problem on these mirrors. As most of the cars that these parts belong to have the peeling paint with white oxide forming underneath. But the pits are too deep for filler primer.
1990 VW Jetta GL 1.8L 8V - SOLD
1992 Honda Accord Lx - SOLD frown
1993 Ford Aerostar XL 4L V6 - Retired RIP
2004 SAAB 9-3 ARC 2.0T - Current

#4501312 - 08/29/17 01:17 PM Re: Filling in pitted aluminium? [Re: Mr_Accord]
Linctex Offline

Registered: 12/31/16
Posts: 6186
Loc: Waco, TX
I have had great success filling aluminum pits with JB Weld.

I have saved many an aluminum intake manifold this way.
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#4501416 - 08/29/17 03:15 PM Re: Filling in pitted aluminium? [Re: Mr_Accord]
dparm Offline

Registered: 04/19/10
Posts: 13521
Loc: Chicago, IL
Whatever you end up doing, I would consider something like Xpel or a similar clear vinyl on top to provide an extra layer of protection. Mirrors are an "impact area" that tend to take a lot of hits from bugs, rocks, road debris, etc.
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#4501522 - 08/29/17 05:27 PM Re: Filling in pitted aluminium? [Re: Mr_Accord]
CT8 Offline

Registered: 10/09/14
Posts: 11250
Loc: Idaho
Clean and anodize the metal and then use filler and paint.
"Don't let your preconceived notions get in the way of facts."
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#4501549 - 08/29/17 05:58 PM Re: Filling in pitted aluminium? [Re: Mr_Accord]
kc8adu Offline

Registered: 08/02/05
Posts: 897
Loc: dayton oh
a lot of stuff folks think is aluminum is potmetal,zamak,or other zinc alloy.
you might be seeing potmetal cancer,zinc pest,ot other intragranular corrosion.

#4501731 - 08/29/17 08:46 PM Re: Filling in pitted aluminium? [Re: Mr_Accord]
Ducked Offline

Registered: 10/25/12
Posts: 4432
Loc: Taiwan
Use aluminium foil as an abrasive to clean it up and then continue with a binder. I use sunflower or boiled linseed oil as a binder but they take a while to set. An alkyd resin or a varnish might be an alternative.

Pits get filled with aluminium dust from the foil and whatever the base metal is.