Nissan 6 gallon steel gas can in good condition for marine use

[Minoru Osaka]

I was given a 6 gallon heavy-gauge Nissan steel gas can for marine use in excellent condition on the outside, but which has rust on the inside.

First question is obvious - why do they make gas cans out of steel which will rust? Why not put some paint or epoxy on the inside so it won't rust?

Second question is more important (since they made it, and it rusted inside) is can it be saved? The entire inside is rusty, but just fleshy rust. I've flushed it with water a lot but the rust is still on the metal.

I guess I could use phosphoric acid but is there any harm to using gas that comes from a can that has surface rust covering the entire inside surface?

[Scott Dorsey]

Normally people keep gasoline in gas cans, which displaces water and keeps it from rusting. Although these days with gasohol that may be a bit less effective.

--scott

[rbowman]

As long as it is surface rust, no problem. I've used phosphoric acid on rusted motorcycle tanks. It is a frequent enough problem that there are kits available like

There are also latex based sealers that have mixed reviews:

or epoxies:

Personally I use standard hardware store pourable epoxy, the thick kind made for coating bar tops or decoupage projects. Do not use the cheaper polyester resin.

[Xeno]

Ever heard of anti-rust alloy coatings? You might find this of interest.

There are a number of chemicals you can use to clean the rust from the inside of a fuel tank, the most obvious one being a mix of vinegar and baking soda. It's a safe method of chemical rust removal and involves mixing vinegar and baking soda to almost fill the tank. Let the mixture sit until it bubbles and begins to change colour with the rust particles. Rinse the mixture thoroughly.

If you have surface rust, it means that the protective coating has gone. Any new formation of surface rust could, and will, flake off and damage carburettor and fuel injection systems. If you manage to clean off the rust, you really need to reinstate the protective coating on the inside. There seem to be plenty of products available for this purpose, just ensure they are compatible with the fuel you are using.

[Minoru Osaka]

I actually had thought about that when I remembered that I had an old jar of phosphoric acid in my chemistry kit which I haven't opened up in years.

I ran an experiment on an old rusty pair of shears left outside too long. The phosphoric acid turned the metal from pure rust to black "something". I don't know what that "something" is, but it's black, whatever it is.

I guess I was supposed to wash it off but I just left it on. Is it too late to wash it off two days later?

The black is all dry now. Not wet. I guess I can scrape it off. Maybe.

I'm thinking maybe I can pure some of the thick clear phosphoric acid into the gas can and shake it around, but I only have about two ounces left.

I've had it in a labeled glass jar for so long I forgot how I acquired it.

[micky]

I had a motorcycle that hadn't been ridden for 35 years. It has rust in the gas tank. I think what I read said to put metal bolts in the tank, add kerosene, do the hootche-kootchie and shake it all around.

I did that, until when I poured out the kerosene it just looked like kerosene. Then I put the bike back tother and it ran a little bit, but it was too much for me and I gave it away. I don't know for sure that I wouldn't clogged the carb, but I was confident at the time.

[rbowman]

That's a phosphate coating that helps retard rust.

Had you used hydrochloric acid it would have also removed the rust but after you washed it off an left the shears to dry they would almost immediately been covered with rust.

[AMuzi]

The black coating is iron phosphate which is much more stable than iron oxide. That's a common treatment for bare steel before painting and not very different from other stable surface treatments such as gun blue.

I have no idea if that's a good idea for a gas can.

There are tank coating systems which are excellent:

Usually used where an original replacement tank is rare or expensive. For a six gallon portable tank you could replace it with a brand new steel tank for less money and time:

(polyethylene tanks are about $20 less)

No wrong answers, name your poison.

[Minoru Osaka]

Thank you for that chemistry suggestion. I think I'll use up the last couple of ounces of the thick syrupy phosphoric acid and let it go black.

I don't know of iron phosphate is soluble in gasoline or not.

Oh my. Over a hundred dollars. I see what you mean. I can understand how that matters for a car gas tank, but not a portable container.

A brand new fuel tank is around that price (uninstalled of course).

That $80 used marine gas tank is EXACTLY what mine looks like. A handle. A large fill opening. A gauge with the fuel level. And a small vacuum-sized hose coming out of the gauge with a petcock.

I don't need all that marine stuff. I only need the fill hole. All those other openings are just another place for the fuel to leak out.

I just wanted to use it as a sturdy sun-resistant outdoor gas tank. I only need six gallons (it's illegal to fill more than six at a time). Most gas cans in the stores are only five gallons and they're square.

I like either a jerry can shape (long & rectangular) or this marine shape.

[Michael Trew]

When you put something in to strip it, perhaps even CLR mixed with water, add a cheap dollar store bag of marbles. Marbles will agitate the mix and rust, and add a mechanical factor to help remove it -- bonus, unlike rocks, is that marbles slide out easily when done.