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Re: POR-15 (was Re: [T3] Painting Front Beam)

In a message dated 6/3/05 9:59:25 PM Eastern Daylight Time, 
topnotch@nycap.rr.com writes:

<< Daryl makes an important point that I may have missed, if you sandblast and
 get rid of ALL the rust, POR 15 is an excellent top coat, if you wire brush
 all but the loose rust will still be there and continue to rust under the
 15, so if you blast dont let new rust set in, and on a humid day... it may
 only take an hour. >>

This was what I was meaning by properly prepping the surfaces (sandblasting). 
I've found that POR15 needs something to grab to in order to stay put. If you 
also use their metal prep treatment, then you add some zinc to the rusty 
surface that helps slow the rusting. The problem is, you're still painting over 
rust, and if it's deep it'll just continue at a slower pace. We used it on a 
utility trailer that stays exposed to the outside elements all the time. On it we 
used all new metal to build it, and then prepped it using their metal prep to 
make the new metal rust. This light layer of rust gave the POR something to 
grab to. It's been in use for over 5 years, and only where we actually 
scratched the surface down to the metal did it start to rust. That rust is only where 
the scratch is, and hasn't grown at all.

On another note, we also did a GM truck frame using conventional auto paint 
and primers. On it we sandblasted the frame and primed it with epoxy primer, 
then spayed K-36 primer-surfacer over it then sanded it smooth and shot it with 
Deltron paint and clear coated it. This has held up as good as the POR did, 
and still looks great after 6 years of being exposed to Michigan winters. :O  I 
think the key is the surface prep though, as you really need to get rid of the 
rust in order to seal it from the elements.  I just did something similar to 
my wife's "new" 90 GMC van, in that I scuffed the bottom of it, sprayed epoxy 
primer then painted it with deltron and clear coated it. This should give it 
some protection from the Michigan road salt, as it doesn't allow the salt spray 
access to the weld seams. We'll see how this holds up in a couple of years, 
but it should help slow the rust down. :D

Bob 65 Notch S w/ Sunroof
       71 Square, now a 2 seat Roadster, pics can be seen at; 

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