Gas Tank Rust - Phosphoric Acid vs Evapo-Rust?

[jbird7262]

Is it best to seal the tank after de-rusting and risk the coating pelling off down the road, one of my tanks looks like leaves floating around when I fill up, yes I do run an in-line filter on that tank, but I have a replacement tank that just has some minor flecking and surface rust, so would just cleaning with one of the above chemicals do and just fill it up and ride, I have all new seals for the sending unit and overflow.

 

[Chuck78]

That's what I am doing now. I was rushed & didn't have enough time to do a prior job until the third time. I had originally dumped the Phos acid out, flushed with gas & acetone, let sit. Bad idea. Scaley black stuff formed overnight. Re-did, flushed with tons of water & a little baking soda to neutralize the acid, dried with hair dryer. It flash rusted from the rapid evaporation with the dryer.
3rd time I wasn't rushed, flushed acid with bunch of hot water, dumped in 93% osopropyl alcohol solution to absorb the water from the seams etc, then flushed with some more gas, then filled with gas. No flash rusting, still sparkling clean 2 weeks later.

It was never really determined if there is any factory coating on the tanks or not, but there doesn't appear to be unless it is something like galvanizing but unnoticeable compared to bare metal. My wife's flat black Rat paintjob on her tank somehow peeled off sitting in the garage unheated during this past severely harsh winter. Spring came & we uncovered the bikes to find an 11"x7" patch of bare gas tank with paint chips all around. Early to mid spring, not much humidity yet, but the bare metal had zero rust and zero paint on the exterior at least.

 

[XR750]

I haven't tried this yet, but dairy farms use a phosphoric acid solution to dissolve milk stones (Cacium???), and it can be used to dissolve calcium deposits inside coffee brewer water reservoirs. Relatively cheap in price, assume it to be food grade safe.

http://t.tractorsupply.com/en/store/dairyland-milkstone-remover--acid-rinse

i haved used TSP for a neutralizing wash after muriatic acid and never had flash rust.

 

[barnbiketom]

The BEST/cheepest/easiest RESULTS I have is with CHEEP toilet bowl cleaner NOT 'the works'
SNO BOWL is the ultimate if you can find it, if not, then the cheep $1.50 stuff at dollar store.
2 bottles.. 10 minutes and good to go.
TRY IT

 

[Grimly]

Right, I remember now, we can't get Phosphoris acid in Canada best we have is Vinegar.......

Can't you get it for hydroponic purposes?
http://www.ebay.co.uk/itm/141189657511