OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk Electrolysis Rust Removal

http://htpaa.org.au/resources/rust-removal

There has been some mention of the electrolysis rust removal method around here
before and I came across this quite well written explanation so thought I'd try
post a link for those who are interested.

Yep, I agree that's a very good article for explaining the process and its issues in layman's terms. And it warns about hydrogen embrittlement, which is all too rare.

Due to the voltage applied, I'm of the opinion that it's really a physical process, where the hydrogen bubbles formed under the rust layer pop flakes of rust off the surface.

I would add that it's important to 'passivate' the metal surface quickly after it comes out of the bath. Or it will form surface rust incredibly quickly, once it's cleaned...

If you have a big enough container, the simplest way is to boil [using rainwater, or demineralised/distilled water] or steam the article for 15 min or so.

Another way is to paint/swab the item with dilute [~5%] Phosphoric Acid, then rinse off with water. This will form a grey iron phosphate protective surface coating.

This statement regarding the 'molasses bath' method is also correct:
I found out this week, that a couple of light gauge steel items I'd put in my molasses bath a few months back and forgotten about, had been in too long... Oh well, nothing irreplaceable!

Any thoughts about the best way to clean up a rusty fuel tank guys? And how to treat it afterwards?

I'm mates with a local stock feeder and they buy molasses in the 1000 litre pods and decant it. To decant it they turn the tap on and let the molasses run into a piece of guttering with a few holes in it that they place the bottles under. Apparently the guttering is eaten away surprisingly fast.

For a gas tank I'd try reversing the electrolysis procedure as mentioned at the bottom of the article for cannon barrels. Perhaps use the phosphoric acid Gadge spoke of and swill it around.

Slash, over the years I have seen great results using both methods on motorcycle tanks. Then it depends on the value of the tank as to the treatment you seal it with after the rust has been removed. The POR15 sealer costs around $100 for the smaller kit

Internal fuel tank rust can be a real trap, as it often conceals pitting that has nearly gone though the metal. So when the rust is removed, you get pinhole leaks.

There are commercial tank prep/lining kits around, mainly intended for motorcycle tank repair. They tend to be a bit exy to use on a mower though - around the $75 mark or so. POR15, Kreem and KBS are a few of the kit brands.

The prep steps for these are 1. Wash out thoroughly with degreaser 2. Wash out with detergent and hot water, and rinse out thoroughly with water. 3. Etch/rust removal with acid solution, rinse out thoroughly once more.

Just looked at the MSDS for the acid etch solution for a couple of them, and they are essentially diluted Phosphoric Acid, sometimes with a small amount of Nitric Acid. Many of the commercial rust removers are Phosphoric Acid based.

Picture 1 & 2 A mower wheel as removed

Picture 3, 4 5. In electrolyses bath running just over 8 amps
And video of action

Picture 6 After about 6hrs removed and water jet blasted

Picture 7,8 Result of being jet blasted, the darker is more of a stain not rust

Picture 9 Glass bead blasted with a fine bead unlike sand blasting this does no pit the surface just cleans it

Picture 9, 10 result of glass bead blasting a nice clean surface not a pitted surface like sand blasting would do

Picture 11 Painted with Etch Primer bought from Super Auto when on special

Just like new.
Just remember if you leave that alligator clip connection submersed it will dissolve too. Did you get much pitting from the bath? I have read that much above 2 amps and it will work faster but can cause deep pitting.

""Just like new.
Just remember if you leave that alligator clip connection submersed it will dissolve too. Did you get much pitting from the bath? I have read that much above 2 amps and it will work faster but can cause deep pitting.":"

I have being do this for about 25 years with the same alligator clips and at 8mps
PITTING ??? it does not eat the metal you wont get pitting
All it does is form Hydrogen bubbles on the GOOD steel and everything outside that is pushed of by the bubbles

I would like to know where you read this:-
I have read that much above 2 amps and it will work faster but can cause deep pitting.

Where you will get pitting if have the current going the wrong way
The + must got to the Anode the - must got to the job

I use vinegar a lot for cleaning up rusty steel parts. Don't use on aluminium parts. It takes time, sometimes a long time, but it always works. Give it time, vinegar ALWAYS works.
Then give the parts a wash with water. Then I mix up some strong bicarbonate soda in water in a spray mister bottle and give it a good coating until it drips off. This is not really necessary but it basically just neutralizes any left over acidity from pits and crevices. Rinse off again with water.
Next I wipe down the object thoroughly with straight methylated spirits on a cloth. This always works for me. Any remaining rust gets wiped off.
Then before any flash rusting has time to re-appear, I spray the whole thing with rust converter. After that you can put on a primer, then put the enamel straight on. Anyway this is what has always worked for me.