I'm planning to build a new black/grey water tank for my '78 Newell. A friend told me that the original tanks that Newell made were of 1/8" mild steel. If I build a tank of mild steel I'm thinking of trying to coat the inside to resist corrosion. Does anybody know if Newell did anything on the original tanks or if I should coat this one. Anybody got any suggestions for what to coat it with?