Posted by Brian in Oregon on July 29, 1999 at 13:37:56:
For bare metal, Rodda makes a product called "Barrier III". It is a primer that is usually sprayed on, but it can also be brushed or rolled on. It can be sanded, though it is not as easy as sandable primer. The paint is meant to replace red lead or zonc chromate type primers. It helps prevent rust and seals light rust (emphasis on 'light'). It needs to be painted over with the final paint of your choice. I've used the original product (just plain Barrier in those days) and it took several years of outdoor exposure to final have rust show through, and even then only in thin areas. Thicker areas are just like new. BTW, unlike Rustoleum and similar paints, Barrier has no fish oil or similar oils in it, so you don't get the annoying pinpricks in the final paint you use.
It comes in gray, green, black and red oxide. $25/gallon.