>
> This is an interesting issue. I don't know if it is still true, but
> solutions like Metalprep used to recommend a final wash with water after
> the metalprep application. This always left the metal discolored. This
> might have been a rust-inhibiting phosphate treatment, as advertised, but
> it looked a lot like rust to me. When a surface is freshly sandblasted, I
> prime it as soon as possible--within minutes if possible. I do not treat
> it with anything, and I most especially do not use anything that
> recommends a final water wash.
>
> I could be wrong, though. I remember I was, once, back in 1963.
Yes, this is rather annoying, I agree. But I've done the Metalprep
treatment/water rinse to pieces and left them for months with this
"rust" looking finish on them and didn't noticeable any increase in the
deposit. I certainly wouldn't paint over something left that long
without re-treatment but it does seem to provide rust protection for
unpainted pieces that are going to be left for a while. My guess is
that iron oxide isn't the only reddish-orange compound of iron. It's
just a pity that it looks so damn much like rust. I've notice that the
"organic" rust removers I've tried leave a similar coating
In stark contrast, do the same thing with HCl (muriatic acid). You can
almost see the rust forming when you're done. Within a few days the
piece will be covered with thick crusty deposit of rust.
Roland
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