Gas Tank Rust - Phosphoric Acid vs Evapo-Rust?

[Chuck78]

Alright so what I've gathered from this is that EvapoRust or Phosphoric Acid products are the best bet depending on how quick you want the job done vs toxicity. No go on muriatic, vinegar was far too slow, & both of those flash rust A LOT very immediately. I thought metal rescue was basically the same as Evapo-Rust but I'm glad you chimed in.

[Andrew Vanis]

I had very good luck with electrolysis (wrap the anode with several winds of plastic window screen to provide the necessary gap)

The rust removal yielded several pinholes. would be a shame to have acid or expensive cleaner drain out of those as it did its magic. Electrolysis liquid (electrolyte) is cheap and not harmful. What ever you us, put the tank over a plastic bin big enough to catch what ever might drip.

not yet on a tank but definitely on other things - have used metal rescue with extremely good results. It is also a non-issue if you get it on the paint. Metal rescue also has a motorcycle cleaning how-to- http://www.metalrescue.com/assets/pd...te%20Paper.pdf

Hint - also what might be helpful on the metal rescue (since it is $25/gal but it is reusable so that price is ok) - expand its volume with a filler. Fill the tank with gravel and then Metal Rescue. I just had to do some larger odd shaped pieces. It would have taken a five gallon bucket to get them covered. I put them in a plastic filing bin and then filled the bin with gravel from the driveway (after giving it a good clean) and it only took a gallon and a half to cover the item and gravel. Worked dandy. When done, took the gravel out and put the Metal Rescue back in the container for next project. The items came out perfectly clean.

FWIW - If I had to do it again, I'd probably do the electrolysis again. cheap, easy, no downside - kinda like me and I like the science of it. a very close second would be the metal rescue with the filler.

[Chuck78]

The creativity in coming up with sacrificial anode insulators is making me reconsider electrolysis, but the effectiveness of that method wanes with the further distance areas from the electrode. I did my old 4:1 this way, and had to move the anode all over the place to get it somewhat evenly treated. And it doesn't really get rid of the rusty spots, it more so converts them, but not the deep scaly parts (or in the seams of a gas tank).

[Andrew Vanis]

The creativity in coming up with sacrificial anode insulators is making me reconsider electrolysis, but the effectiveness of that method wanes with the further distance areas from the electrode. I did my old 4:1 this way, and had to move the anode all over the place to get it somewhat evenly treated. And it doesn't really get rid of the rusty spots, it more so converts them, but not the deep scaly parts (or in the seams of a gas tank).

In my experience the further spots just need more time. since electrolysis doesn't affect the good metal the longer time isn't an issue. In my case I had a good bit of rust in the back corner from sitting on the side stand so put the anode there and by the time that part was cleaned the rest of the tank was good too. Scope camera was a nice find on clearance @ home depot that let me see all the way in the back corners.

same for the rusty seams. If water (electrolyte) can get there it will get cleaned. It could take a couple of days. fast, cheap, good, pick two (learned that here on GSR) I don't know what you mean my converting the rusty spots, I have never experienced that. in my various electrolysis work my rust got removed from the item and suspended into the electrolyte or attached to the anode.

BTW re:your 4:1 (exhaust I'm guessing) On my chrome exhaust i found and used wood bleach Oxalic Acid. Another cheap rust removing bath. http://www.how-to-build-hotrods.com/remove-rust.html I documented it here a couple years ago. Just submerged my headers/pipes a couple days later all shiny and all the mini rust in the pitting was gone. no buffing required. still looks good today. Better living through chemistry.

[chucksuki]

I used evaporust on mine 3 years ago. Still perfectly clean metal inside. It didn't harm the paint at all and I saved it and used it with great success on various projects over the years.

[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