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Zinc-rich paint
Posted: Fri May 30, 2008 6:31 pm
by chimpboy
Just curious, that zinc-rich paint for "cold galvanizing"... designed I think for steel.
If that were used on aluminium, would it tend to make the total package more resistant to corrosion or actually more prone to corrosion?
Posted: Fri May 30, 2008 6:47 pm
by v6hilux
No, only the zinc, until it is all gone, then then the alloy corrodes. If you are only using paint instead of a large ingot of zinc, don't expect too much protection.
I know that that alloy outboard motors have anodes;
From the interweb;
Commonly-known metals are ranked in terms of 'nobility', with gold being at the top and zinc near the bottom. This nobility ranking refers to the metal's ability to resist galvanic corrosion.
The less noble the metal, the more easily it will corrode. If more than one type of metal is involved in the corrosion process, the least noble metal will corrode first. So, introducing an ignoble metal into the process stops the electron transfer between the differing component metals that need to be protected. For example, if stainless-steel and bronze components are immersed in seawater, the less-noble bronze will surrender its electrons to the seawater, corroding away in the process.
Does the bus have an alloy brake pedal?
Posted: Fri May 30, 2008 7:07 pm
by KiwiBacon
Aluminium corrosion isn't normally a problem as the oxidation layer protects the metal underneath.
It's only in really aggressive environments you'll have issues. Like sea-spray or chemical attack..
Posted: Fri May 30, 2008 7:10 pm
by ssfabricator
dont paint aluminium with cold gal you will get electrolisis (ignore the spelling)
Posted: Fri May 30, 2008 8:05 pm
by v6hilux
Re: Zinc-rich paint
Posted: Tue Jun 03, 2008 12:59 am
by sudso
chimpboy wrote:Just curious, that zinc-rich paint for "cold galvanizing"... designed I think for steel.
If that were used on aluminium, would it tend to make the total package more resistant to corrosion or actually more prone to corrosion?
Why use anything? Aluminium IS resistant to corrosion. Its only when exposed to certain chemicals or elements that generate electrolysis that will corrode it.
Whats it being used for?
Cold galv paint is ok for temporary protection of bare metal but it still needs to be top coated for longer term protection.