Author Topic: Electrolysis (Read 10173 times)

julianf · « **on:** April 25, 2016, 12:58:21 PM »

Been somthing ive been wanting to try for a while, and accquired a rusty fuel tank at the weekend, so -

Cut out the worst with a friends plasma, but its the seams that i know will leak - and sorting them with the rust present wont be easy.

PAT test fail psu from the skip at my parnters work (cracked casing - i just wont stick my fingers in there)

It was all fizzing this morning, so ill see what it looks like tonight - im only doing half the tank at a time, so as its easier to move, and less electrolyte to deal with.

Keef · « **Reply #1 on:** April 25, 2016, 01:41:19 PM »

My son did this with a 70s motorbike fuel tank he is restoring as the inside was rusty. It worked really well.

Julian · « **Reply #2 on:** April 25, 2016, 03:17:02 PM »

Really great project and I'll be most interested to see the outcome, but I can't help but think you'r on a hiding to nothing with the seams looking like that.

Given the simplicity of the tank ... guessing it's off a Land Rover, wouldn't it be easier to make a new one? Steel can be had quite cheaply if you buy and old CH storage tank. I got one circa 4 foot cubed for a fiver and the steel will be way thicker than the original.

That said, awaiting the results with great interest.

julianf · « **Reply #3 on:** April 25, 2016, 03:29:32 PM »

It all just depends on how it comes out. Ive seen some borderline unbelievable stuff on the web - things like bolts that just look like lumps of brown stuff still having threads underneath, etc.

If it comes out with ragged but shiny seams, then it wont be much bother to re-flow them (i understand that theyre soldered, not welded) but if it still looks manky, i wont bother trying.

Its something ive been wanting to give a try, so this was an opportunity - if it does not work on the tank, nothing much lost.

K.H · « **Reply #4 on:** April 25, 2016, 06:35:02 PM »

Will follow this with interest

knighty · « **Reply #5 on:** April 25, 2016, 06:38:41 PM »

ohhhh, I've been wanting to give it a go too

some of the photos/videos online make it look pretty impressive

Julian · « **Reply #6 on:** April 27, 2016, 10:40:20 PM »

Well, I got fed up with waiting for the results and advise!

A quick look on the web pointed to washing soda and a battery charger. Didn't have any washing soda but by chance I did have some sodium hydroxide kicking around, so today I had a play ...

It's only been running for an afternoon, but the results are quite impressive ...

My battery charger was getting quite warm running at 5-6 amps for several hours as was the electrolyte!

Julian · « **Reply #7 on:** April 28, 2016, 07:59:19 PM »

Sorry Julian ... not internationally hijacking the thread, but I had quite an urgent need to clean up these mower components.

So, and up date ... this is great at removing rust, but where the rust was it leaves and black deposit which in it's self seems to be quite tough, but it can be removed by vigorous abrading with Scotch-brite or similar.

Given time it appears to lift paint too. Paint removal is greatly helped by periodic scraping.

The resulting surface appears to take paint really well.

Julian ... what electrolyte did you use and is it leaving the same black deposit as I'm getting?

julianf · « **Reply #8 on:** April 28, 2016, 08:18:52 PM »

I don't mind. Its just a breath of fresh air when people don't claim themselves to be experts immediately...

Here are some photos -

Im using naoh also. Added bonus of removing paint, however, im surprised that my anode still has paint on it.

As you can see in the photos, the black stuff is present also. It looks very much like the black that you get from phosphoric acid treatment also.

Im not sure how repairable this tank is. Or rather if its worth the effort. I thought id just remove the rust and then weld it up, but its soldered together, so the remaining solder will contaminate the weld.

I know its a simple design, but you can buy them off the shelf and someone half-inched my cut up oil tank....

Julian · « **Reply #9 on:** April 28, 2016, 09:21:24 PM »

Seems to have done quite a good job for you. I might see if can get hold of some washing soda to see if it still results in the black deposit. And yes, I remember using some rust "eater" product that claimed to turn rust into something else said to protect the steel ... that gave a similar black finish.

I ran the battery charger on its high setting today ... it settled at 8 amps and seemed to work quicker. I've started eyeing up my arc welder that has a lowest setting of 30 amps ... what could possibly go wrong!

Another thing I’ve noticed is that the current seems to take the shortest path through the electrolyte (seem sort of logical I guess). I fitted two anodes in diagonally opposite corners, but I'm wondering if more, movable anodes would give a better coverage on the item being cleaned,

On the tank issue what if you cut the sides off getting rid of the seams then weld on new sides. It would reduce the capacity a little, but would be doable.

julianf · « **Reply #10 on:** April 28, 2016, 10:04:14 PM »

Ive not been sure as to if the electrons / ions take line of sight, and then just 'short' out on the clean metal, or if they do the closest bit first, and then move onto the further bits.

I kind of think the latter, as i cant see how i would have managed to derust the ends of the tank otherwise. But the line of sight stuff is certainly done first.

Its not a bad idea trimming the tank. One end of it is done for also. As you say though, probably not hard to fab up another one - im borrowing a friends plasma at the moment, but, like i say, my flat packed oil tank went walk about...

Ill see what comes up.

This tank is for under the seat on the 110 csw defender. You cant fit 'normal' tanks in there, as they all have the fillers pointing out to the back. This is a millitary one, with the filler in the top.

...but if i get to fabricating a new tank, ill probably just use a 90 tank, and move the filler (which would be easier than making a whole new mod style one)

Julian · « **Reply #11 on:** April 28, 2016, 10:49:48 PM »

I didn't mean line of sight exclusively, but it was noticeable the closest parts appeared to get cleaned quickest.

oakwoodtv · « **Reply #12 on:** April 28, 2016, 10:59:26 PM »

Elecrierty always takes the line of least resistance.

greasemonkey · « **Reply #13 on:** April 29, 2016, 07:22:19 AM »

That's might interesting.
I've just bought a vintage cement mixer. Freakishly heavy, and covered in a good layer of rust.

I'd need a 45gallon drum full of liquid. It's not going to go in whole, (I'd need an IBC full for that) but I was going to strip it anyway.

The rust converter is Vactan, or a few other names.
I think it's phosphoric acid, but my mind isn't quite functioning properly yet. Could be something else.
It does give a hard black finish, which is surprisingly resistant, but not actually a finish in itself.
I love the stuff, used loads of it. It's not cheap though, and it doesn't go very far.
For bigger projects, this is a lot better idea.

julianf · « **Reply #14 on:** April 29, 2016, 09:18:54 AM »

Quote from: oakwoodtv on April 28, 2016, 10:59:26 PM

Elecrierty always takes the line of least resistance.

Yep, path of least resistance... but to where! : )

For example, if you have a tube, with a closed end, and rust on the inner face of the closed end, the current will, first, pass to the closest parts.

But, when its de-oxidised the closest (path of least resistance) parts, will it then either -

a) short to the clean metal thats closest, or
b) go a longer distance for a favorable reaction

In my vast experience, its not entirely clear cut!

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