I am not a fan of the Por 15 type products. No, bondo requires a very clean
surface to stick to. I think if you need a product like Por 15, what you really
need is a more thorough cleaning. I prefer a chemical dip to clean things up.
Pitting is the worst thing that can happen with a chemical dip, but certainly
nothing the primer cannot handle. What will that Por 15 be like in 15 or 20
years? Will it peel or fall off like cheap Japanese bondo or will it stick like
good bondo on a properly preped surface?
new mexico jim
"BORDER,RYAN (HP-FtCollins,ex1)" wrote:
> I just went through this on my rear fender project (still underway). I used
> a good scraper knife with straight razor blades. I bought a pack of 100
> razor blades for about $5 at harbor freight and went to town. Sometimes I
> used a heat gun to soften things up a bit though only when necessary, as
> scraping it off cold doesn't leave a residue, using a heat gun tends to. I
> didn't have too much undercoating; and probably broke 10-15 razor blades in
> the process.
>
> Next I scrubbed the whole thing out with a stiff wire brush and a hose-
> getting everything as clean as possible. Next step is to Por-15 the
> underside of everything. Which actually brings me to a question: I cover
> the back-side of all my welded areas with fiber-glass re-enforced bondo. I
> use a disk sander to rough it out, but go ahead and leave it built up just a
> little to help strengthen the area. The area around the weld is typically
> surface rusted a bit; which the POR15 really likes to stick to. The POR15
> also seems to stick really well to the bondo. But, I'm a bit perplexed
> about what to do in the area right around the weld:
>
> 1) Bondo over surface rust, POR15 over bondo... will the bondo stick to the
> slightly rusted surface OK? Will it continue to rust with a layer of bondo
> between the POR15 and the metal?
>
> 2) Sandblast area, bondo and then POR15. Seems this might hurt the adhesion
> of the POR15 to the metal in the area surrounding the bondo patch. And, I
> hate to sandblast of a layer of metal in an already weakened (welded,
> ground-down) area.
>
> 3) POR15 and then bondo (then maybe POR15 again). Will bondo stick to
> POR15 OK? Will the POR15 stick well to freshly welded and ground metal (and
> in many cases brand new metal patch panels). My experience has been that
> POR15 really doesn't like to stick to new metal very well.
>
> Up until now, I've been going with #1...
>
> Ryan.
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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