[Tripower455]

Has anyone ever used ospho to etch bare rust free metal, prior to using POR-15? Also can you weld through ospho?

[Tripower455]

Has anyone ever used ospho to etch bare rust free metal, prior to using POR-15? Also can you weld through ospho?

[rickschabener]

Understand that I am not a body man, but, I have used Ospho to convert slight surface rust-it seems to work. When I tried the same thing on bare metal, it took forever to dry. In fact it never did. I had to wipe it off.

[Marty Phipps]

I've used Oshpo too many times, and I hate the stuff.
It's supposed to be used on rust, to convert it.
If you use it on clean bare metal, you'll have major adhesion problems.
A friend of mine had his boat trailer sand blasted a few years back.
By the time we got it to my shop, surface rust had already started to show.
Sprayed it with ospho, wiped down the excess, let it dry.
Sprayed on sealer, then paint.
First time in the water, the paint fell off.
Under that was a ton of corrosion.
Next time, one of my techs. used ospho on an old 41 chev. that suffered from small cancer spots.
He couldn't afford to have the rust removed, so we blasted what we could, and treated the remainder with ospho.
Used long and strong on the holes.
The ospho reacted and caused the filler to fail as soon as paint was applied.
Por 15 doesn't need any treatment under it.
Blast what you can, scrape the rest and spray, or brush the por 15 on.

[72LeMConvt]

Wow, and I've had the exact opposite results!

When I rebuilt the front end on my '72 a few years back, I sandblasted upper & lower control arms. Before surface rust set in, I used Ospho. It turned the light gray blasted areas a darker gray, and turned some areas that still had specks of rust (I wasn't a thorough blaster, then [img]smile.gif[/img] ) black. After 24 hours or so to dry, I then brushed on Rustoleum Semi-Gloss black right from a can.

I've had absolutely no problems since.

Of course, I may have bad corrosion under the paint and not know it....

Kirk