From: MV (MV@dc9.tzo.com)
Date: Thu May 19 2005 - 09:37:45 PDT
Coal tar epoxy has very high dielectric strength, meaning that it
doesn't conduct electricity well at all. General Motors use to use it
on the inside of their Elpo diptanks, but at that time (20+ yrs ago),
the steel had to be blasted to a white finish - no rust allowed. This
other product mentioned is quite different than regular coal tar epoxy.
My experience with coatings vs treatments has been that the treatments
work well (most are very similar - the Duro, Rustoleum type converters)
if the rust is not heavy and flaking. If the rust is heavy, it has to
be removed at least to get the flakes off so another preparation can be
used. If the flakes are left - you will end up with a bad job.
Sandblasting works great to brush blast surfaces so you can use a
conversion coating or a good paint primer. I've had good luck with
sandblasting down to a surface of spotty white metal, but with some pits
left in it and rust shadows. (Blasting to white metal takes a lot of
sand and time and isn't worth it IMO.) Then priming with a Rustoleum
type rusty metal primer and topcoating with an industrial enamel. I
have a trailer frame I did this with 17 years ago and the paint on the
undercarriage looks like I painted it last year. The paint exposed to
the UV rays, has deteriorated somewhat and should be recoated, but rust
is not coming through anywhere.
I've heard good things about POR paint also, but it is expensive. I
just sand blasted a truck frame and bed and part of a large trailer
frame and went through 800 lbs of sand. That's about $64 and 3 hours of
blasting. I then primed it with 4 gallons of Rustoleum type rusty
metal primer (actually made by Valspar) - about $70. 3-4 gallons of
finish coat will go on top of that - another $70.
I don't know what POR is going for right now, but 4 gallons of that
stuff would be expensive, plus spraying is not an option apparently. I
would not want to brush on 3-4 gallons of paint! Talk about a time
eater. I also question the ability to use POR over flaking rust.
Doesn't sound like a good solution. If the rust is flaking - I believe
it needs to be blasted or mechanically removed. Then conversion
coatings or primer can be used with success, which are much cheaper than
POR. So what do you use POR for? I have never tried POR and that may
be why. I guess if money is no object or not a major consideration,
then things may be different.
AutoZone is selling a conversion type product now for about $5.00/qt.
I've seen it for even less at farm type stores.
FWIW,
Dave
santoken@bright.net wrote:
> In this case, I'd use Ensign 395A. As I stated in an earlier email, it's pretty impressive stuff. I had a guy tell me that when it cured, he couldn't weld through it...don't know, never tried it myself.
>
> Kent
>
>
>>From: Recovry4x4@aol.com
>>Date: Thu May 19, 7:12 AM
>>To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
>>Subject: Re: [MV] Rust 'Treatments' vs. 'Coatings'
>>
>>I was going to use Chassis Saver on the inside of my pipeline deuce frame.
>>It's along the lines of POR-15. Now maybe they've chnaged over the years but I
>>was warned many years ago that POR-15 in ultraviolet sensitive and needs to be
>>topcoated. I'm not overly particular about the texture of the inside of the
>>frame but I only want to do this once. Any thoughts?
>>Kenny
>>
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>
>
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