Re: Treatment for rust inside metal gas tanks?
I clean them out w/battery acid, flush them w/ water and look inside w/a flashlight; if not totally clean I put the acid back in let it sit some more. If you don't treat it with something it will rust up again pretty quick. I've had a couple that I did this to, and even following w/a baking soda and water mix, if I let them sit a week? I gotta repeat the acid.
I found the best coating to be Bill Hirsch, they are the only one that certifies comatibility with E 85; the thing being that even if you don't run E 85 there is "some" alcohol in all gas now a days and that alcohol will eventually eat most of the other coatings, they don't say either way whether alcohol laced gas will screw up their coatings; it does on some.
I have also used KREEM, big with the motorcycle guys and had good luck but have heard others say that they have had it peel and clog strainers and filters.
Judging by my luck w/POR 15 on "accessible" surfaces ("can we say mixed bag") if it holds up great. but I have seen it "not" stick and peel right off too. and this is on 2 parts treated the same way at the same time out of the same batch. considering the hassle and potential issues with it peeling off the inside of a tank, IDK if I want to chance it.
IDK what the name of this other product is, "red" something or other, that I have heard great stuff about, them and Hirsch I have heard the least complaints about possible problems about; I will try some of the "red" (I think it's "Indian Red" or "red Indian" or something like that)
but; I took a 3 qt tank off a 5HP Briggs horiz engine (the style where the carb mounts to the tank and has 2 tubes protruding into the tank) to the local radiator shop; he raked me for $50 for that 3 qt tank!!! IDK what product he utilizes. I bought a qt of the Hirsch stuff and have done 6-7 tanks so far from that one quart. The one taht cost me $50 was on my Trac vac which is the most "seasonal" piece I have and sits the most from one leaf season to the next vs a mower, snow blower etc.
On my harley golf cart that I had given to me, the PO had had the tank steamed cleaned by another radiator shop in town but did not get it coated. this tank is ~2-1/2 gallons I guess; it has not yet had gas put into it since he had it cleaned, but he gave me the reciept for having had it done within 2 weeks prior to abandoning ship on that project (I have since found and solved his problem that made him give up on it) and saw that this other shopp charged him $50 just to steam it clean. YIKES!
SO, since I had the Bill Hirsch stuff here anyway, I took advantage of its fresh-clean-and not-yet-had-gas-in-it condition and coated it. It sticks great to freshly cleaned tanks.