RUST, bloody rust. And phosphoric acid.

I've got a tank with rust that I can't shift. Strange because it really isn't a thick coating but it's really clinging to the steel. See pic below.

So far I've tried (and failed with) white vinegar and nails and Por 15 (the whole caboodle).

Now I've moved on to phosphoric acid. How long do you guys let it soak in your tank, and what's your process following the draining of the acid? I was just gunna rinse it out with water and then swish some 2 stroke around.

Cheers fam.

At the risk of repeating myself, http://www.realclassic.co.uk/techfiles/petrol_tank_cleaning_and_rust_removal.html

worked for me. start at post #431

http://www.dotheton.com/forum/index.php?topic=64973.420

semmins said:

At the risk of repeating myself, http://www.realclassic.co.uk/techfiles/petrol_tank_cleaning_and_rust_removal.html

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Thanks. I found this page a couple of weeks ago and have not been able to find it since! It's not exactly what I was talking about in my original post though.

Safe

hurco550 said:

worked for me. start at post #431

http://www.dotheton.com/forum/index.php?topic=64973.420

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Thanks Hurco. Is it safe to leave the acid in the tank until all rust has been removed, or is it better to limit it to just a couple of hours?

AND, do I need to dry the tank out completely before adding the 2 stroke, or can it still be wet?

what I used was basically metal rescue. Devient may chime in soon, he has had a ton of luck with phosphoric acid, and I will probably use it on my next tank. I left what I used sit over night. I will say, the acid will eat aluminum, so make a block off plug instead of using your aluminum petcock.

Yes, it needs to be dry before coating with oil. After treatment, I used about a gallon of hot water mixed with baking soda to neutralize whatever kinda acid was in my bath. Sloshed out and rinsed with hot water to get all the soda out. I then put a few quarts of denatured alcohol in to bond with the water and "dry" it out. after that, a bit of time with a shop vac and compressed air to actually get all of the moisture out. once it was dry, I immediately sloshed and thoroughly coated with two cycle oil.

Just make sure you have everything on hand when it comes time to take the acid out. If not, it will rust before you know what happened. Don't wanna have to be running into the hardware store while your tank is sitting there flash rusting =P

Great advice, thank you. And yeah it was Deviant who originally inspired me to try the acid as he seems to be so happy with it. I guess I'll find out!

Thanks again.

I used Kleen Prep and Etch from Home Depot. My tank was pretty bad so I let it soak overnight, drained and filtered and put it back in the tank over a 3 day period. After the 3rd day I added some nuts and drywall screws and about a quart of the PA and shook it every 15 min for a couple of hours. Rinsed with water and baking soda, then denatured alcohol and finally gas/2 stroke mix like above post stated. The Phosphoric Acid leaves a residue that is supposed to slow the flash rust.

I've had excellent luck with the Klean Strip Phosphoric Prep and Etch from Home Depot, too. It's a solution of about 40% acid to water. You can cut it with water and leave it in longer if you want. The last tank I did, I used about a liter of etch and a half a box of roofing nails. Shook it up for a few minutes, let it sit for an hour, shook it up again and it came out spic and span. Then I rinse with water. And follow up with isopropyl alcohol. Then a heat gun to dry.


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No Prep & Etch here in the UK. Or at least not the stuff you guys get from Home Depot.

el barto said:

No Prep & Etch here in the UK. Or at least not the stuff you guys get from Home Depot.

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http://www.amazon.co.uk/Rust-Off-Phosphoric-Remover-Descaler/dp/B00BP60ULM

The MSDS shows that Rust Off is 40% phosphoric acid and 1% alcohol, so it's chemically equivalent.

deviant said:

http://www.amazon.co.uk/Rust-Off-Phosphoric-Remover-Descaler/dp/B00BP60ULM

The MSDS shows that Rust Off is 40% phosphoric acid and 1% alcohol, so it's chemically equivalent.

Click to expand...

Oh cool, thanks. I actually picked this up a few days ago and got started with it yesterday. Tank's sparkling now...

Just a quick follow up on this for those that might be looking to de-rust their tanks. As mentioned earlier, this was my third attempt at the job and at last results! Although I didn't dry the tank until it was absolutely bone dry, which I think will come back to haunt me in the foreseeable future. However, three days on it's looking ok.

First I poured two litres of phosphoric acid into the tank (got it off eBay for £9 plus shipping I think). After about 2 hours I began to see some positive results, about half the rust had gone, so I kept it going for another 2 hours. I agitated it every hour or so and changed the tank's position - upside down etc. By this point it was late and I couldn't be bothered to do any more so I went to bed. In the morning the rust had completely disappeared - hurrah! The acid was drained and the tank rinsed with some water and baking soda (just in case, not sure whether this actually has any effect). I then throughly rinsed the tank with more water and drained it as much as possible.

Next up was drying. With no heat gun to hand I used a hairdryer, not ideal but whatever. It took probably 4 hours of the hairdryer blasting into the tank to get it dry, although I could still see small wet patches in the corners at the front of the tank. Again, it was getting late so I gave it a thorough coating of 2 stroke oil and it's been sitting ever since, although I have been agitating it every now and again. Below is a pic of the tank as it is now. The metal is slightly darker because of the oil, but there's no rust, and hopefully flash rust will be minimal.

Thanks for all suggestions/tips etc.

Excellent.

Looks great man! Glad it worked out for you =)

Thanks for your help fellas