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Filling in pitted aluminium? #4501227
08/29/17 10:44 AM
08/29/17 10:44 AM
Joined: Jan 2007
Posts: 450
LBP
Mr_Accord Offline OP
Mr_Accord  Offline OP
Joined: Jan 2007
Posts: 450
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?

Thanks

Last edited by Mr_Accord; 08/29/17 10:45 AM.

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
Re: Filling in pitted aluminium? [Re: Mr_Accord] #4501231
08/29/17 10:49 AM
08/29/17 10:49 AM
Joined: May 2013
Posts: 2,162
Saskatchewan, Canada
Johnny2Bad Offline
Johnny2Bad  Offline
Joined: May 2013
Posts: 2,162
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.


'57 FL Straight 50 wt
'90 Miata 1.8L w/Rotrex Supercharger [Mobil1 0W-40]
'96 Ram 1500 [3.7L Mobil1 0W-20 / 1L 15W-50]
'01 PT Cruiser [Mobil1 0W-40]
Re: Filling in pitted aluminium? [Re: Johnny2Bad] #4501248
08/29/17 11:27 AM
08/29/17 11:27 AM
Joined: Jan 2007
Posts: 450
LBP
Mr_Accord Offline OP
Mr_Accord  Offline OP
Joined: Jan 2007
Posts: 450
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
Re: Filling in pitted aluminium? [Re: Mr_Accord] #4501312
08/29/17 12:17 PM
08/29/17 12:17 PM
Joined: Dec 2016
Posts: 7,417
Waco, TX
Linctex Offline
Linctex  Offline
Joined: Dec 2016
Posts: 7,417
Waco, TX
I have had great success filling aluminum pits with JB Weld.

I have saved many an aluminum intake manifold this way.


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: Filling in pitted aluminium? [Re: Mr_Accord] #4501416
08/29/17 02:15 PM
08/29/17 02:15 PM
Joined: Apr 2010
Posts: 13,537
Chicago, IL
dparm Offline
dparm  Offline
Joined: Apr 2010
Posts: 13,537
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.


2017 Chevrolet Corvette Grand Sport
Re: Filling in pitted aluminium? [Re: Mr_Accord] #4501522
08/29/17 04:27 PM
08/29/17 04:27 PM
Joined: Oct 2014
Posts: 12,698
Idaho
CT8 Offline
CT8  Offline
Joined: Oct 2014
Posts: 12,698
Idaho
Clean and anodize the metal and then use filler and paint.


2015 Ford F150 2.7
2018 Ford F350 6.2
Re: Filling in pitted aluminium? [Re: Mr_Accord] #4501549
08/29/17 04:58 PM
08/29/17 04:58 PM
Joined: Aug 2005
Posts: 924
dayton oh
kc8adu Offline
kc8adu  Offline
Joined: Aug 2005
Posts: 924
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.

Re: Filling in pitted aluminium? [Re: Mr_Accord] #4501731
08/29/17 07:46 PM
08/29/17 07:46 PM
Joined: Oct 2012
Posts: 4,825
Taiwan
Ducked Offline
Ducked  Offline
Joined: Oct 2012
Posts: 4,825
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.


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