Stop the old oil change arguments...here's the scoop "Matthew T. Russotto" <russotto@grace.speakeasy.net> wrote in message
news:nYadnaOdydk3aI7bnZ2dnUVZ_v6tnZ2d@speakeasy.ne t...
> In article <460E256D.90D3DD91@m>,
> Eeyore <rabbitsfriendsandrelations@m> wrote:
> >
> >> And, if you get ONE scratch on it, it
> >> rusts.
> >
> >No it doesn't. Even if the scratch goes down to base metal.
As long as there is a substantial coating of metallic zinc in the
near vicinity of the scratch, the rust will be inhibited. This is
a very basic premise in cathodic protection. Zinc is higher on the
electromotive series than iron, which means it will be sacrificed
in the corrosion reaction before the iron is.
Now, I'll freely admit, a daub of zinc in the center of a mile of exposed
steel will not hold the mark. Other factors are in play when you are
so far overbalanced.
With regard to ternplate (steel coated with lead, in this example) the
steel will not corrode as long as the lead coating is intact. Lead is
BELOW steel in the electromotive series. As soon as penetration
through the lead coating reaches the iron or steel layer, corrosion
can not only occur (a suitable electrolyte being present) it will be
ferocious, as the ferric alloy is sacrificed to the protection of the
lead. |