I was at a 'It's a Beautiful Day' concert in 1970, on acid, so I guess
I'm an Electrochemist responding to Andrew's request! Please, no calls
until after 1300 hrs!!

Miguel

On Sun, Aug 16, 2009 at 9:39 AM, Alistair Bell<albell@shaw.ca> wrote:
> 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).
>