Preventing rust in gas tank in storage

Stabil makes a fogging oil. I drain tanks every winter and give them a few squirts after drying.

Saber said:

There seems to be a lot of products and chemicals to get rid of the rust. I find the challenge is in rinsing those items out and getting the tank dry from the rinse before she starts rusting again.

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I've seen the suggestion of washing out with diesel, then petrol, rather than water. Not tried it.

I did a tank clean-out two years ago and ran into the issue I mentioned above. I was successful cleaning up the bad stuff that was in there as a result of sitting for 30 years. It flash rusted a little but I was anxious to get on with the painting and riding the bike. I have the tank off for other reasons this winter so I decided to do another clean-out to take care of the little bit of rust I still see in the tank. I did the vinegar fill and soak & sloshed with screws inside. Last night I dumped the vinegar (tank looked awesome inside), rinsed with garden hose 5 times to get the rust particles out, ran the heat gun in the filler hole to dry it up - instant flash rust again! The whole process was about 15-20 min. So I re-filled with fresh vinegar and am now contemplating my next move. I have spent many hours researching this forum and everything else available on the internet. I don't need perfect, I just want to take the best shot at minimizing the flash rust as I finish this clean-out. I am not interested in starting over with different products or methods. I don't want to get into sealing the tank at this time either. Some options I am considering:
1) with just flash rust, my rinse will be faster (1 rinse out instead of 5) so may be able to minimize the time between vinegar dump and hot air drying.
2) rinse with diesel or kerosene instead of water.
3) add a denatured alcohol rinse right after water rinse.
4) add a baking soda rinse - but I am not convinced neutralizing the acid is the problem.

I welcome your input!

Tom

You will need to coat bare steel with something else it will rust again pretty quickly. Some of the rust converter products will leave a phosphor coating behind that will inhibit further rusting.

I remember when I painted my car years ago, after sanding the hood to bare metal I rinsed the dust off with a garden hose. Even though I dried it with towels, the hood rusted within an hour.

Yes for sure. Getting to the coating step without rust is the hard part.

There is a product called Chemprime, which is a phosphoric acid rust remover, but unlike other rust removers, puts a molecular level zinc-strontium rust inhibitor on the iron surface.

Do not rinse, but allow to air dry. The rust inhitor conversion occurs on drying.

I used it on my Atlas tank, no problems after 7 or so years.

Slick

texasSlick said:

There is a product called Chemprime, which is a phosphoric acid rust remover, but unlike other rust removers, puts a molecular level zinc-strontium rust inhibitor on the iron surface.

Do not rinse, but allow to air dry. The rust inhitor conversion occurs on drying.

I used it on my Atlas tank, no problems after 7 or so years.

Slick

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There are many products on the market used to prepare metal surfaces for painting. What most have in common is having phosphoric acid as a component in their "formula". The phosphoric acid chemically reacts with rust to leave a "pickled" surface which is resistant to rust. I very
successfully used a product called OSPHO in several tanks.

I also wonder what the bugaboo is about flash rust. It is an extremely thin layer of surface oxidation and isn't prone to continuing through
the sheet metal like some cancer. Rust damage in fuel tanks occur at the bottom of the tanks where water has accumulated over the
course of years. The cure for this is to use a fuel stabilizing product like STABIL and/or totally emptying and drying the tank every year
or two.

Thank you gentlemen. The phosphoric approach sounds interesting. To go with the Chemprime or OSPHO, do you have recommended steps to get from current situation of a tank full of vinegar to end result of a clean tank? Also, I don't want to harm the paint on the outside of the tank so any precautions there would be appreciated.

I agree, minor flash rust would probably be ok. I had no issues with it after the last tank clean. Just thought I would ask in case there's an easy fix to avoid seeing it every time I refuel.

Seems to me that any derust treatment that is then washed out leaving bare, non altered steel surface will allow new rust to form. Not sure why anyone is worried about that as this is how the tanks came from factory and have lasted many decades with or without use. As soon as you start using petrol you introduce condensation at the upper level of the tank and light rust will form. If this causes loss of sleep, then best to research tank lining options and be done with it.

What's really needed is a de rusting agent that will last for decades and will not be diluted/washed off with petrol.
Afraid nothing comes to mind.

Bernhard said:

What's really needed is a de rusting agent that will last for decades and will not be diluted/washed off with petrol.
Afraid nothing comes to mind.

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Something like nickel or even chrome plating inside of tank might work.
But I keep coming back to how tanks, untreated, can last decades. This is kind of my overall philisophy on these machines, if it has stayed functional for 30 or 40 yrs, something must be right with it?

Maybe it's the Ethel in the fuel? (joke!)

I had just filled up a roadster tank with oxalic acid ( 600g oxalic powder mixed with 5l of hot water ) , started this morning , flushed around 5/6 times , will see tomerrow .......that tank was rusty inside , so first a handfull of screws to get rid of what could be taken off ...........may be , will try phosphoric after , if not satisfied with the previous trial, will keep you informed.

Initially getting rid of the rust is fairly straightforward. I used distilled white vinegar and after 24 hours it was rust free. But I rinsed it out with water and dried with a hair dryer. All in the house, but still had flash rusting. It' was only superficial, so not concerned. But, I've since been told about rinsing the acid vinegar out with diesel, then petrol.

The specialist tank de-rusting products appear to give up to 6 months protection, which should avoid flash rusting before you use the tank again. But alone, they are not a long term rust inhibitor. They need painting or coating.