The picture below is of oxidative polymerization ("chicken skin") in the inside of the tank I that formerly used for WVO (front tank, 1994 F250 7.3 IDI NA ) . I used a DIY Hotfox style coolant heated fuel pickup . This setup was used for about 3 1/2 years . I am now usng a polyethylene tank for WVO .
Consider using an aluminum, plastic , stainless tank to avoid polymerization problems .