There are 2 very different methods of galvanizing commonly used. One is
the hot dip galvanizing used mostly on nails and similar applications
where appearance doesn't matter the part is dipped in a molten tin zinc
mixture. The other is electro galvanizing which leaves a smooth finish
like you see on furnace pipes, garbage cans, etc. This method is what
the auto manufacturers use but it has a flaw that is common to most
plating applications that use an anode, when you have complex shapes
like a car body you get anode shadowing. This is when the side of the
part facing away from the plating anode receives little if any plating
(boxed in parts or folded fender lips). An excellent example of anode
shadowing is the back of a chrome bumper, there is always a much thinner
layer of plating on the back unless the plating shop flips the bumper
around during the plating process( they charge extra for this). The
other catch is how long do they plate the part this controls the
thickness of the plating and the cost.
There is an entire industry out there dedicated to cathodic protection
of equipment it's an expensive process that requires a lot of up keep
but for pipelines and off shore oil rigs it's the worth the money. I've
never seen one of those car protection kits that had any form of
sacrificial anode as part of the kit so I don't see how they could do
anything but erode cash from your wallet. The industrial systems work by
applying a charge between the part you are protecting( the cathode ) and
a sacrificial anode while they sit in some form of electrolyte( water,
soil, etc. ) thus almost all the erosion will take place on the anode
and protect the the equipment, that's the readers digest version of it
there is allot of engineering and maintenance required to make it work.
There has to be something sacrificial for rust protection to work, an
anode (electrolytic protection) or the galvanized coating.
my $0.02 on the subject
Doug Hamilton
1960 TR3A
1963 Fiat Cabriolet
>Date: Mon, 11 Mar 2002 10:42:27 EST
>From: ZoboHerald@aol.com
>Subject: Re: rust removal / rust prevention
>
>Someone wrote:
>
>>>> > Many (most?) modern cars are galvanised and will not rust, with or
>without
>>>> > electronic corrosion protection....
>>>
>
>Perhaps the galvanizing process varies depending upon who does it, or perhaps
>it has gotten better in recent years? One of the "selling points" of the 1974
>Volvo my mom bought new was that the sheet metal was all galvanized (in
>addition to all of the wonderful Volvo undercoating/rustproofing). Well, maybe
>the Belgian Volvo assembly plant didn't do all that good a job (no offense to
>any Belgian listers -- and Belgian-built Triumphs always seemed to hold up
>about as well rust-wise as any other Triumphs). That Volvo was seriously rusty
>within about five years, much more so than any of the earlier Volvos I owned
>at the same time.
>
>On the other hand, I've some fairly old galvanized buckets, garbage cans and
>washtubs around and about the barn (from its dairy cow and horse days).
>They're still in pretty good shape. [;-)]
>
>- --Andy Mace
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