Using concrete and metal prep on inside of gas tank

I have a small 2-3 gallon metal gas tank that goes with a Miller
Welder and Onan engine. The tank was empty for many years and
the inside has/had rust in it.
I cleaned the varnish out first then tried various liquids to handle the
rust. I finally put a cup of gas in the tank along with about 45 steel
nuts. I shook it around for about and hour until it cleaned up pretty
well. Flushed with gas and denatured alcohol to get the rust residue
out.
I then took about a cup or so of Klein Strip Concrete and Metal Prep
and poured it in the tank and rolled it around to cover all surfaces . It
is suppose to remove the rust and prevent the rust from returning. I
had used this previously on a little yard trailer and it seemed to work.
On that project I just painted it on and then after a day wire brushed it
off and painted the surface.
On this project you can only pour the metal prep into the tank and roll
it around to cover all surfaces and pour the excess out. So now I am
wondering what will Happen when I put gas back in the tank.
chemical reaction? Thoughts?

I have done that but flushed it out first with mineral spirits then a little gasoline before filling it. Seems to have worked as gas in the sediment bowl is clear and no rust. The long term is still to be decided.

Rather than create a bad situation, Put some of the concrete cleaner on a ceramic (discardable) surface and add the gasoline to it. Personally I would rinse the cleaner out with water, then heat dry the tank with a blow dryer. I might even put a sealer in the tank to prevent further rust. Jim

you need a caustic solution to clean it just like the rad and machine shops use to clean stuff such as engine blocks also. or else a steamer will work good also. i have done it both ways. when done with steaming pour in some menthol hydrate and it will take care of the left over moisture.

Am i the only that thinks shaking metal pieces around inside gas tank with vapors is a death wish??

Just kinda curious what happened to a product called Kreeme,that was suppose to be the final step,for coating the insides, maybe its obselete now ??

Yes

Chemistry 101
Rust is an oxidation reaction producing Iron oxide(rust)
4Fe + 3O2 + 6H2O 4Fe (OH)3

Returning Rust back to iron is called reduction.
Here are the equations for the reaction: Iron (III) oxide + carbon iron + carbon dioxide 2Fe2O3(s) + 3C (s) 4Fe (l) + 3CO2(g) In this reaction, the iron (III) oxide is reduced to iron, and the carbon is oxidised to carbon dioxide.

What is the best acid to reduce rust?

What is the best way to remove rust from an iron?
Phosphoric acid will remove rust and create a rust resistant (relative) layer.

If you want to clean the iron surface, you can indeed use an acid but it is important to use a corrosion inhibitor, so that only the oxide is removed but the metal is never attacked. You can use HCl with hexamethylenetetramine previously dissolved inside.

Cheapest place to buy phosphoric acid??

Amazon is my friend;
1 Gallon 85% Food Grade Phosphoric Acid Rust Remover Clean Etch Metal
Brand: Duda Energy
4.8 out of 5 stars 166 ratings
Amazon's
Choice
for phosphoric acid cleaner
Price: $50.35 ($0.39 / Fl Oz)

Miracle Sealants PHOSGAL4 Phosphoric Acid Cleaners, Gallon
4.5 out of 5 stars 39
$40.00

I went to college to become a chemical engineer. Changed majors after one year. My sinuses couldn't stand the smell of the chem lab.

Other acids will reduce rust, however to my limited chemistry background, phosphoric acid will reduce rust and leave a black coating which is supposed to prevent rust from removing.

Please seek a chemistry opinion. I'm a chemistry major dropout.

I would fill the tank with a dilute solution of phosphoric acid and water and let it sit for a while.

My advice is worth what you are paying for it!!!

This ends class on Iron Oxide. Test tomorrow.

MY MAN GEORGE you are spot on , looks like that is the solution ..

For drying out a tank I use the shop vac set on blow. They dry very quickly.

Have you checked price and availability of a anew tank?

Your time and peace of mind are worth something. Tanks are thin, rust may have eaten away so much a good cleaning may start a leak.

I've fought rusty tanks before, end result, the rust came back, got tired of fooling with it and bought a new one. Done!

Jerry
Buy the expensive metal preps. The smell of phosphorus acid smells like baby vomit.
You can pay more for baby vomit or go to Amazon and buy a gallon

Geo how about oxalic acid I use it to clean iron out of my water filters works great

X2 GEORGE! CM

All that work on no liner : (...

Like posted. Any acid will reduce rust.
Don't know if it will help prevent future rust like Phosphoric acid will. If it turns rust black, it might work.
Ask a real chemist, I'm a dropout.

my goto is a product called Ospho. Phosphoric acid and other stuff. removes light rust and converts deeper rust then leaves a protective coating. Use it on all the sheet metal.. most paint or hardware stores have it..

I used Kreeme on a JD B about 30 years ago and it still looks good with no sign of rust.
I cleaned the tank with diluted muriatic acid.

Stay away from acids. Tumble it with gravel or nuts or something to get what will loosen. Then put EvapoRust in and let it soak. Turn it to get all the inside surfaces.

Klean Strip Concrete & Metal Prep IS phosphoric acid.

The expensive metal preps have phosphoric acid as the active
ingredient.
Once you smell phosphoric acid, you will never forget it.
Buy the strong stuff, a gallon of 85% is $50 from amazon.
Shop around on Amazon and you may find it cheaper. I have a new
gallon sitting on the shelf for my next project.
The price may vary depending on concentration.

Muriatic acid, plumber's acid, hydrochloric acid are the same acid. Muriatic acid will take your breath away, you can see the chlorine bubbling off. Don't breathe the fumes. It can damage lungs.

That said. Muriatic acid is very cheap. If you use it be careful. Problem, muriatic acid and possible other acids will also attack the metal.
Phosphoric acid only attacks the rust.

MTjohnso, you have done about the best that you possibly can using the phosphoric acid. I use it a lot in preparing rusted parts for painting. I always rinse aggressively with plain water because that is what the instructions with the particular product that I use recommend.

BonepartSouth, that is the FIRST thing I thought of.

BonepartSouth, that is the FIRST thing I thought of.