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Discussion Starter · #1 ·
Hello to All,

Im repainting some outdoor porch lights and cannot seem to remove what appears to be like a white oxidized power under the paint.

I have removed the paint w drill & circular rotating brush, and a hand brush. The i took an old terri-cloth towel, submerged in water, removed excess water and s rubbed the light. When light was wet, it darkened the white powder. But, as soon as it dried, it lightened up again. I installed the lights in 2002. They still work fine and are all covered by 10’ porch so no direct rain or sun.

Is there a chemical or something I can apply to remove white powder? Anything else? As we all know, need a good clean surface for new paint.

thank you in advance.

Happy Thanksgiving to all !
 

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I just finished one very similar to that one. . . . it is cast pot-metal. the cheapest form of metal there is.
(remove it from the wall and take it apart) soak it in straight vinegar for half an hour, (place it in a plastic bag and rotate it every few minutes. rinse well with the garden hose sprayer. (yes, the socket will get wet, but it will dry out eventually. best to remove it, if you can).
apply a metal primer that states "for rust and corrosion" - then your choice of spray enamel. (I prefer Rust-Oleum).
 

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Discussion Starter · #5 ·
PS - looked up the definition of cast pot- metal:

Pot metal—also known as monkey metal, white metal, or die-cast zinc—is a colloquial term that refers to alloys of low-melting point metals that manufacturers use to make fast, inexpensive castings.

I would guess that a low concentration acid, acetic acid, etches off any powder residual, yes?
 

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Discussion Starter · #7 ·
yes - clean, prime, paint and call it a day.
I’ll post a few after pics. Might be a couple of weeks until I can get back there, but will do. Also, I hit them all again w circular wire brush & drill and took off a lot more of powder, then rubbed down w wet Terri cloth towel. Wish I would have known then to use acetic acid…but know now
 

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just treat it like oxidized or corroded aluminum and you will be golden.
not to over-think it, because it is only a porch light. but, if you had many to do or other, bigger projects, this is the procedure I would use: vinegar wash, rinse, ospho overnight, prime with the appropriate primer that contains Zinc Chromate or etching primer, and topcoat enamel. this would be for people that have aluminum boats or old cars with pot-metal parts like door handles and window regulator knobs. this is just for informational purposes only for larger projects as it could get expensive putting all these things together for just a one-time small project.
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