Re: Those black spots on the metal. What is that?



Doug Miller wrote:

In article <IlpOg.5160$TA5.4437@fed1read09>, "Jim Hall" <jimhall.@xxxxxxx> wrote:
A disease.? Granted I beat up on that old Stanley chisel building fences, a
deck and a shed and there was a neglected rust spot on it for awhile. But I
cleaned it up along time ago. Now the metal at that spot has sort of eroded
away a little and there's a black spot there. Doesn't look like rust.. I
sanded on it today with some wet and dry sand paper some came off. What's
with the black. Is this black rust?

It's iron oxide.

Contrary to popular belief, rust and iron oxide are in fact not the same
thing. Rust is *hydrated* iron oxide (iron oxide plus water). When iron or
steel gets wet and begins to rust, it's actually a two-step process: the water
accelerates the formation of iron oxide -- which is black -- and then combines
with the top layer it to form rust. When you remove the rust, there's still
going to be a spot of black iron oxide beneath it.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Accually there are 2 forms of iron oxide one of which appears black and inhibits
further oxidation and one that is orange and promotes further oxidation. Water is
not necessary.

ron

.

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