glock

a couple of questions for guys who have used por15 before ... underside floor pans had rust and couple of other spots to, i wire wheeled all rust areas ,and planning to por15 whole underside of car (i have the trans and rear end removed) now there is alot of spots where i didnt have any rust,like trans tunnel and above gas tank and support rails, is ok to scuff up with a wire wheel the painted areas under the car and use marine clean and metal prep or do i have to remove all painted areas to bare metal ? also do you have to use chassis black after por15 ( the car is never in snow or rain )

fireturd350

iTrader: (8)

You want to knock off all the scale rust.

Most of the questions can be answered here:
http://advanced-rust-protection.com/porstordosan.html

stealtht/a

iTrader: (1)

You can't put POR 15 over paint. If the paint is well bonded to the metal and you scuff it well it is ok to paint over very small areas of paint, but otherwise, it's going to peel off.
Just use the POR 15 in the bare areas and paint over the scuffed paint with a similar epoxy primer. Overlap the primer over the POR 15 after you sand the edge of the POR 15, just a quarter inch or so.
You don't need the chassis coat on the underside, no uv exposure there. The uv just causes it to fade a little, doesn't break it down. They now make POR 15 in gray that is pretty close to the factory primer.