I bought a Paughco Porkster tank off of eBay. The ad proudly said it had been treated with Kreem. When it arrived you could tell that after the Kreem was used the tank had never been opened. I wanted to feel the lineing so I stuck my finger inside and felt around...the Kreem was lifting off the steel in big patches. I contacted the seller, he wanted me to send the tank back for a refund. I said no, I wasn't going to pay $20 to get back $60 which would have ment I would be shelling out $40 to get back $40.
I put 20 feet of towchain into the tank and shook the tank for 10 minutes knocking off the loose Kreem. With the oil mix a tank wont rust anyway.
I just can't recommend Kreem after THAT experience