Fuel tank for a 20

[sailcat]

I am in the process of rebuilding my 72 (20'). After pulling the floor up I had a local tank builder measure the space I had from the rear of the CC, forward to the casting platform. I was able to get a 75 gal. under the deck. I wanted as much weight forward as poss. because of the 200hp going on the back.

[Blue]

Luthers quoted me $560 for a new tank so I'm going to fix my old one. Its not too bad off. What are they coated with to protect them??