Folks,
If I remember my metallurgy lectures at university, internal rusting
without air can be caused by air moving over the outside surface of a metal
so that a bolt could be rusted right in deep just by exposing its
head. And the head need not rust. It's called anaerobic
rusting. Slightly different type of rust as one is by oxidation and the
other by electrolysis. However, I stand to be corrected as metallurgy was
a side subject and was soon forgotten.
At 03:11 PM 5/31/01 -0700, Roland Dudley wrote:
>Two comments. Rust can't continue without oxygen. If rust continues
>under POR-15, then it doesn't form an air tight seal. However, I can't
>say whether POR-15's claim that it does seal, is true or not. I suppose
>one could come up with some sort of experiment to prove this one way or
>another.
>
>If I recall, the manufacturers of POR-15 recommends treating the surface
>prior to painting with their brand of acid prep, which I strongly suspect
>is phosphoric acid based. I'd be surprised to learn that POR-15 wouldn't
>stick to a surface prepared with their own product.
>
>Roland
>
>
> > Hi,
> >
> > Among the responses to my "Brushing vs Spraying" question, I received
> some interesting responses about using POR-15 on the backside of the
> rust-free steel sheet metal wings on my Healey. In the past, I've heard
> or read only positive testimonials about this product, but now I'm
> hearing some things to the contrary. One person indicated that the
> product seals in any oxidation, and that it (rust) will continue to
> progress underneath the coating, contrary to what the manufacturer
> claims. Another person indicated that they were told the product might
> not adhere to the zinc phosphate coating left behind by phosphoric acid
> such as used by Redi-Strip, or Oxysolve like products. I've always been
> told the zinc phosphate coating was a very desireable surface for a
> coating like paint or primer. Judging by my past experiences with
> POR-15, I can't imagine it NOT adhering to this type of surface. It sure
> sticks to everything else it comes in contact with.
> >
> > Anyone like to shed some light on this?
> >
> > Thanks,
> >
> > Scott Helms
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