Fuel Tank - Internal De-rusting by Electrolysis?

[jymphil]

There is much information for de-rusting by electrolysis on-line, but has anyone here tried it on the internal rust of a Minor fuel tank.
Is it practical with a Minor tank? If so was it successful? What anode material was used: iron/steel or carbon/graphite or what?
Can anyone advise please?

[charlie_morris_minor]

I think it might be difficult..

for electrolysis to work best you need a clear line of sight between the cathode and annode.

Therefore you will have to put something down the filler neck or through the fuel gauge sender.. neither of which is very large and once in side the tank you need to ensure the two never touch or you will short everything out needless to say.

I am not saying it is not possible just that i would not want to to do it..

as for the anode i tend to use a pair of old disc brakes i have lying around.. just clean them regularly with a metal kitchen scouring pad

[jymphil]

Thanks for your reply, I've left it some time before responding hoping to have more replies, but it looks like I shall have to sort it out for myself as there seems to be minimal MM experience with this technique. I hope to 'report' on how it goes - if it goes!

[bmcecosse]

Waiting with interest for your report - take some pictures if you can please ! Before and after inside the tank would be useful..

[chickenjohn]

Just get some phosphoric acid and make up a 5-10% solution in water. Let it soak for a few hours and rinse out, all the rust will be gone and the surface stabilised at least until it is used again. Much easier than electrolysis!

[robedney]

Much easier than electrolysis is to flush the tank with hot water and a good de-greaser, rinse it out and then toss in enough misc. nuts, bolts and screws to cover the bottom (you'll have to shake them past the baffle into the section that has no opening). Now pour in half a gallon or so of Ospho (or any similar product) and seal up the filler pipe and sensor hole with good duct tape (good -- not cheap -- duct tape will stick well if you clean the surfaces well first). Ospho is a pre-diluted/mixed solution phosphoric acid. The solution bonds with the iron (in the rust) to form iron phospate, which does not expand and flake off like iron oxide (rust). Now rattle away, or pay a couple of kids to roll it around on the back lawn. I rattled mine by making a jury-rigged shaker table using a drill press and some bungy chords. The screws/nuts/bolts will abrade away the loose rust while the Ospho converts the rest to a nice hard surface. Post rattling allow it to sit for awhile, rotating now and then. Flush the whole thing out with a much of a water blast as you can manage (a pressure washer is nice but not mandatory) and shake out all the screws/nuts/bolts. Let it dry inside, then flush once more with water. Check the screen on the bottom of the suction tube -- if it's in nasty shape make a tool with a hook and remove it. It also doesn't hurt to toss a magnet in and center it on the bottom of the tank. Pure, virgin iron oxide (rust) is non-ferrous, but there's very little virginity inside an old Morris tank. An amazing amount of junk will stick to the magnet over time. Make sure that you have a perfect seal when you re-install the fuel level sender!

[bmcecosse]

I think someone strapped it to a cement mixer to do this job. Don't be surprised if this treatment turns the tank into a colander.......

[robedney]

Ah, yes -- the colander problem. I forgot to suggest the very first step, which is to tap over the tank with a hammer first -- not so much as to leave dents, but enough to break free the larger chunks of internal rust and to assess the condition of the steel.

If you have mostly sound metal with a few holes in the bottom you can try visiting your local radiator rebuilder to have them soldered shut. Don't try this yourself unless you fully understand how to prevent blowing yourself up. Or, you can do what I did, which is to take the bottom half (below the seam) to bare steel, coat it with epoxy, embed some fiberglass cloth -- including extra layers where the holes are -- and add another coat of epoxy. The right sort of epoxy/glass composite has been used to make gas tanks, so this is a safe bet. If you want details about how to do this correctly feel free to contact me. In normal use -- meaning fairly frequent driving -- this sort of repair ought to last a good long time -- and the outside bottom of the tank will be thoroughly rust proof.

There are various kits around to coat the inside of gas tanks. I wouldn't use one. I've some experience with steel and rust.

[MarkyB]

The right sort of epoxy/glass composite has been used to make gas tanks"

From what I understand the ethanol they are putting more of in petrol is having a disastrous effect on fibre glass tanks.
http://www.burtonbikebits.net/ethanol-in-fuels.htm

[bmcecosse]

I would also be afraid that a fairly light knock (flying stone/bump on kerb etc) would shock the resin free of the tank with resultant possibly severe leakage. I appreciate that over the pond new fuel tanks are probably few and far between/jolly expensive - but in the UK they are readily available and not TOO expensive. Painted up on the outside a new one should last for a good 40 years - provided left FULL over long periods of non-use. Some folks on the TR7 forum swear by a coating of POR 15 on the inside of the tank - don't fancy it myself - but then I do have a good spare tank in my garage loft, so it's not a priority for me at the moment! And yes - I had to buy a new tank for my TR7 - £180 and a nightmare to fit!

[GPO_Van]

HI all
I tried to put a link on from a site describing (with pictures) how to de rust a petrol tank using electrolysis' unfortunately it is no longer on the internet, but I had copied the info and pasted into a word Doc.
If any one wants it PM me with your email address.
I also have a Utube link below de rusting an engine mounting.
Regards
Reg
http://www.youtube.com/watch?v=R5I5WBG5HPw

[charlie_morris_minor]

you have a PM

[robedney]

One of the things I do when I'm not under my moggie is make carbon fiber violins. I also live on a big steel boat and have been working with coatings for years now. Two things: I would only do with with a specific brand of epoxy resin, and definitely not polyester resin. Secondly, prep is everything. If the bare metal is properly prepped before the first coat of epoxy resin, and the subsequent coatings (to fill the weave of the applied glass cloth) are timed correctly (so as to chemically bond with the first coat) you could wack the tank with a sledgehammer and not dislodge the epoxy/glass composite. In fact, that composite will be there long after the rest of the steel rusts out. I've seen steel boats run up on the rocks with this sort of coating system remaining intact. The problem with stuff like POR 15 is that it's on the inside of the tank where -- given time -- some amount of free water is inevitable. All you need is one very small coating void -- or a crack -- to allow water infiltration, and rusting will start in time. As steel converts to iron oxide it expands dramatically, disrupting any coating on top of it. Pretty soon you've got flakes in your petrol. So, a perfectly applied POR 15 coating might last indefinitely -- but the trick is getting a perfect coating on the interior of a tank, where you can't see a lot of the surface in the first place. If the POR 15 coating starts to fail in -- let's say a decade -- there are going to be a lot of clogged fuel lines. It might be a fab product -- I'm not saying it isn't -- but experience and research warn me off of it.

I totally agree that the best solution is a new tank (if you can find one), and you are absolutely right that keeping the tank topped up in short term storage is the very best way to preserve it. In long term storage, I'd drain the tank and mist the inside very thoroughly with a corrosion resistant spray.

I would also be afraid that a fairly light knock (flying stone/bump on kerb etc) would shock the resin free of the tank with resultant possibly severe leakage. I appreciate that over the pond new fuel tanks are probably few and far between/jolly expensive - but in the UK they are readily available and not TOO expensive. Painted up on the outside a new one should last for a good 40 years - provided left FULL over long periods of non-use. Some folks on the TR7 forum swear by a coating of POR 15 on the inside of the tank - don't fancy it myself - but then I do have a good spare tank in my garage loft, so it's not a priority for me at the moment! And yes - I had to buy a new tank for my TR7 - £180 and a nightmare to fit!

[bmcecosse]

I don't fancy the POR 15 at all - I merely report that the TR7 forum members in USA/Canada seem very enthusiastic about it. But as you say - slightest imperfection and it will be the beginning of the end.......

[charlie_morris_minor]

thank you GPO_Van

I have read the article, certainly answers my concerns,, where to get a vented plastic insert from.. not impossible to make up your own though.

also it shows you how to improve the line of sight between anode and cathode. You just need to ensure that both are not touching and off you go.