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Paint over galvanized parts?

TomMull

Luke Skywalker
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I posted a more car specific question on the lotus forum but in general, does one gain anything by painting galvanized steel parts?
Tom
 

LarryK

Darth Vader
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Biggest problem is getting it to stick.
 

TomMull

Luke Skywalker
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Biggest problem is getting it to stick.
It would appear from what I can find that it it difficult but not impossible to get it to stick. But does one gain anything? That part will be hidden so will not be seen until the next owner replaces it so I'm interested only in corrosion resistance. (I took more than half of the original part out of the car with my shop vac.)
 

Jim_Stevens

Jedi Trainee
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I soak parts in POR15 Metal Ready prep solution and that seems to have worked.
 

TomMull

Luke Skywalker
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That's what the literature says so maybe I'll give it a try although I've never been a fan of POR15
 

Popeye

Jedi Knight
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Dumb question: how are cars with galvanized sheet metal painted?

...found the answer here: https://grassrootsmotorsports.com/forum/off-topic-discussion/painting-galvanized-steel/71891/page1/

Javelin posts, "Ooh, ooh, ask the guy that sells steel for a living!!!

:D

It depends on the galvanizing. Standard galvanized (with "spangle") is coated with zinc in a "hot dip" process. This is a thick coating that leaves a satin, greyish surface. Electrogalv is the same coating, only applied differently, and much, much thinner. This is typically "brighter" and reflective. Neither is suitable for painting whatsoever. Not only will paint not stick to the coating, but sanding the coating is hazardous and you might as well just use regular old hot roll steel (mild steel) if you do that.

Now, Galvalume (or Algalume) is galvanization with 55% aluminum and 45% zinc. Galvalume is much better suited to painting and corrosion resistance. As a bonus, it has some heat-resistant qualities. This is fairly easy to find and only slightly more expensive than regular galvanization.

Lastly is Galvannealed or "Satin Coat". This is a regular hot-dip galvanized 9all zinc) that's immediately heat treated (annealed), which alloys the steel with the zinc. The finish has no spangle and is a dull matte grey finish. This is the galvanization that car manufacturers use. You can weld it and paint it with no ill effects whatsoever. It is also extremely durable, being an actual alloy. This is more expensive, but well worth the money.

Evan: try finding a local to you metal sales place, either a supplier (like what I work for) or a sheetmetal shop. You should be able to buy Galvalume all the way down to 30 gauge (it's very common in the steel siding/roofing industry) and Galvannealed down to 22 gauge.

Hope that helps!"

Now I know!
 

TomMull

Luke Skywalker
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My sills are hot dip galvanize unlike car sheet metal. Still might try the POR15. I can't see that it will do any harm. Tom
 

Popeye

Jedi Knight
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Advice from the Grassroots forum is dipping in muriatic acid to strip the galvanizing. Outside for health and safety reasons. A sill is pretty big, though...
 

Milliecat

Freshman Member
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Hi,
I used to work for a HGV trailer manufacure , and we produced a lot of galvanised and then painted parts and trailers - the galv bits are first given a Mordant solution to clean and etch before paint , see below
Ivan

[h=1]Rustbuster T-Wash Mordant Solution for the Treatment of New Galvanised Surfaces Prior to Painting[/h]
 
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