rust treatment

[Fred]

Hello,

I know you can get a black "paint" to paint over rust, but how does it work and is it any better than using normal gloss paint? Presumably forming a barrier to stop water getting in is half the battle?

The one I have seen is bizarrely water based, I would have thought water is the last thing you want to apply to rust! I know they are not quite the same but the Ronseal and Hammerite metal paints that are supposed to stop rust forming in the first place require a special solvent, don't they.

Thanks.

[meow2222]

The best rust treatments contain phosphoric acid in water. This converts existing rust to a stable compound (iron phosphate I guess).

NT

[Martin Pentreath]

Sounds like Coca Cola to me. At last, a use for the stuff, I certainly wouldn't risk drinking it.

[The Natural Philosopher]

Neither water nor air cause rust. Its both together. Or water plus some other oxidant like whatever seawater has in it.

Eliminate either one and you are on a winner.

[Dave]

But doesn't coca cola rust/rot the gut? I wouldn't risk drinking it either.

Dave

[meow2222]

far too weak unfortunately

NT

[Rod]

Ah - but our CC doesn't contain high fructose corn syrup (like it does over there - but not the passover version IIRC).

[Martin Bonner]

The oxidant in sea-water is just dissolved or entrained air. The reason sea-water is so powerful at rusting is that it contains chloride ions which either make the rust layer more permeable, or catalyze the process (I can't remember which now - it's more than a quarter century since I did Metallurgy!).

Quite - which is why the Titanic hasn't turned into a pile of brown sludge - the air can't get to it, so it doesn't rust.