70Yellowbird

I did a search but couldn't fine anything on this subject … Please help.

I'd like to re-apply the protective coating on the backside of my '70 fuel cap. It's starting to rust through the white coating. Looks like the same coating on the inside of the filler neck also. Is there anything special about this product other than being fuel resistant?

Hammerhead Fred

Pics would help.
Most likely the "white coating" you see is oxidation of the underlying steel which is galvanized. There's no way for you to apply this.

70Yellowbird

Thanks for your reply. I can't post photos because I've already bead blasted. I can only say that it does not look at all like oxidation and looks like white paint. I'm the original owner, so I'm sure these are original.

Hammerhead Fred

Tanks were originally galvanized with a zinc coating (new/reproductions are protected via some type of nickle coating method).
Zinc oxidizes initially into a "white rust" which can look like white paint/powder.
Should you allow it to oxidize further the sacrificial zinc coating is completely consumed and the underlying metal rusts into a traditional red rust.
Sounds like you've now removed the zinc coating and will need to come up with some other method of protecting your cap/neck that will also tolerate the gas fumes and the source of the moisture that caused the original symptoms.

70Yellowbird

Thank you for the education … I've been learning so much here. I'm getting a new tank anyway, but wanted to save the cap. The cap also had the red rust in a few spots, so it was on its way 'out'. Perhaps I'll be saving it on a shelf!