whats it called?? the coating you use inside gas tanks

[butch86]

thanks guys,
i got really lucky. i dropped the tank and the PO must have has the tank cleaned recantly. i pored the 2 to 2 1/2 gallons of gas that was left in the tank through a old tshirt tapped around a 5 gallon bucket. there was only about 4 or 5 little peices of trash. i would sware it was like an old leaf that had parts fall in it. it wasnt matalic in any way. the fuel was also a really pink almost red hugh to it. i am guessing staybill or marvel mystery oil. i washed it with hot water and dawn dishwashing liquid and about 2 cups of purple power. and dumpped it in the same manner and it was clean coming out. i was tickled to get so lucky with a 27 year old truck. i am also assuming its a replacement tank. i blew out the main and return lines and tooj my pressure washer and shot hot water and purple power through the hard lines. all was good there too. i am gonna do one final cleaning with some denatured alcohal i think any suggestions on what to do my final ?