Date:         Sun, 16 Aug 2009 08:39:21 -0700
Reply-To:     Alistair Bell <albell@SHAW.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Alistair Bell <albell@SHAW.CA>
Subject:      Re: Electronic Rustproofing?
Comments: To: Andrew Grebneff <goose1047@GMAIL.COM>
In-Reply-To:  <f700b5ac0908160148yd049591jd22f20499ccd96@mail.gmail.com>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed

Andrew,

your'e wrong here.


It is called galvanizing, whether hot dipped or electroplated. Modern
car makers do use it to some degree or another.

But the important thing you do not understand is the protective
effect of galvanizing has *everything* "to do with electrolysis".

Do more study, you'll find how that the zinc coating acts as the
sacrificial anode when applied to metal, so much that even if the
coating is broken it still protects the un-covered steel.

Mind you it works better on simple structures like anchor chains,
cleats, etc. Less well when the structure is complicated and there
can be localised extreme conditions, as in a car, or a fastener
through differing materials, stray currents at moorages, etc.

Galvanizing works, hot dipped more than electroplated (hot dipped has
more zinc applied).


Alistair



On 16-Aug-09, at 1:48 AM, Andrew Grebneff wrote:



> But VW and the other car companies did the
> next best thing. They started building cars in the 80s with steel
> panels
> coated with a sacrificial anode - it's called zinc plating.

This is NOT galvanizing. Galvanizing is electroplating... what you end
up with is a thin coat of zinc metal (visible as flattened crystals on
the surface) over the base metal. What the carmakers do is to treat
the metal sheet with some chemical, which leaves a residue on the
steel. This is rather ineffective.

Thye purpose of galvanizing has nothing to do with electrolysis. What
it does is merely to keep the steel surface completely away from
water. Nio water, no rust (one form of iron oxide, I think a hydrous
one; as a mineral in nature I think it is limonite).