Earl had...Rust bullet...on the back side of his front bumper. when he sent it to be rechromed, the Lady called him and asked what was on the back side? She said the chrome stripper wouldn't take it off. she now offers it as an option for coating the back side of her rechroming...
here is one place... https://www.summitracing.com/search/brand/rust-bullet I like buying the... rustbullit 6 pack
when i do mine ill use roofing tar thinned with gas until its brushable. gas smell goes away in a few days and its rock hard. cheap too!
I wouldn't use roofing tar,that is nothing but a mess. Then in the future Everytime you work on it you get full of it.nothing but a big mess