Re: [MV] Q: Chemical dipping for MV and M151 A2 Bodies?

From: David Cole (DavidCole@tk7.net)
Date: Mon Jan 19 2004 - 08:33:44 PST


I used to work in a GM Paint Shop years ago outside of Detroit. Our paint
shop had the second Elpo/E-Coat system ever put in place within GM. I
sincerely doubt that any one other than a large scale painting company
could afford an Elpo/E-Coat system. Everything about the system is very
expensive and unless you are dipping many peices per hour (like 60 cars per
hour) the cost would be prohibitive. The paint has to be constantly
agitated, the power supplies are massive and controlled (thousands of amps
at 2 volts, etc) and the paint is expensive and you need thousands of
gallons of it to dip a car body. The process that takes place prior to the
E-Coat dip was called bonderizing (or the bonderite process) at one time.
It is actaully a 7+ step process of mildly acidic washes, rinses, de-
greasing, caustic washes, detergent washes, and finally phosphating in a
certain order to get the right layers of coatings at the surface before the
e-coat. The phosphated surface was fairly rust resistant even before the
E-Coat.

Since this system is pretty much impossible to duplicate, I think most
people are better off blasting rust off mechanically, priming with a self
etching primer and then topcoating. Then going back and applying
rustproofing compounds to the interior areas of the body. Good
rustproofing compound will penetrate and stop rust. I did a test of some
rustproofing compound I had and I put it on some bare metal tags and some
rusted metal tags, nailed them to a tree in my backyard in southern Ohio
(years ago) and left them. Two years later there was no signs of rust at
all on the bare tags and the rust on the rusted tags was stopped and did
not spread. Good rustproofing compound is not cheap, $50+/gallon is not
out of reach, but it is probably money very well spent. Eastwood and JC
Whitney were both selling the same set of rustproofing tools some years ago
and I bought a set from JC Whitney (about $40.00). It's a messy job and it
stinks (literally) but it sure does work. I guess that is why the military
does it also.

Dave

On Sun, 18 Jan 2004 09:28:39 -0500, Ray Fougnier <rfougnier@comcast.net>
wrote:

> Modern auto bodies are spot welded with no coatings. They then go
> through acid dip and an e-coat, which I guess is electically charged
> application. This would cover between welds and all of those places even
> undercoating wouldn;t reach. No piant is ever applied anywhere except
> the external body parts and whatever gets oversprayed. They no longer
> use rust proofing goops like in the 80's. e-coat is dull gray when it
> comes out, ready to be primed/painted.
>
> So, if the dipping that you are looking at is followed up with an e-coat,
> I would say do it. Then you would not have that rustproofing blocking up
> drain holes.
>
> chance wolf wrote:
>
>> ----- Original Message ----- From: "Buzz" <buzz@softcom.net>
>> To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
>> Sent: Saturday, January 17, 2004 9:04 PM
>> Subject: Re: [MV] Q: Chemical dipping for MV and M151 A2 Bodies?
>>
>>
>>
>>> I agree with Joe, "What makes you think they were painted in the first
>>
>> place?"
>>
>> My 151A2 has rustproofing throughout the inside of the channels. My old
>> Renault had a 'coating' on the inside of its channels. I don't imagine
>> either would be well served by having that coating dissolved by a
>> corrosive
>> chemical and left open to the mercy of salt and moisture as bare metal,
>> but
>> as with anything on this list, your mileage may vary.
>>
>>
>>
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>
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>

-- 
Dave


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