DE-Rusting motorcycle a petrol tank with a current

[Gragson]

Got form on many tanks for this, have used electrolysis but I don't like it especially for odd shaped internals like bike tanks, especially if there is some previous sealant goo still attached.
Aggressive (ish) chemicals are more efficient, depending how bad to start, even to the point of needing nuts / bolts / what have you, per the OP internal tank state.
At the point there is hardly anything loose left, I go the POR15 process route but don't use their expensive proprietary chemicals. Replace stage 1 & 2 with (1) hot high strength alkaline cleaner - which is what they lable as massively expensive marine clean, (2) phosphoric diluted solution which is what they label as metal ready, equally expensive - and both stages can take a fair few goes!
What I do rate is their sealer finish, just checked a bike done in 2013 and its still looking good despite the rubbish fuels - a bendy camera stick thing is useful for this, be amazed at how cr@p & rust can still be stuck to low areas you might think are clean.

If they are Krauser panniers on that MZ they are worth more than the bike BTW

 

[Hopefuldave]

Despite what everyone says I use stainless, since that is the cathode. The anode is what you are de-rusting. Current runs from negative to positive pole, hence shouldn't release as any hexavalent chrome ( if existing).

It does though, it's the positive electrode and chromium is more reactive than iron (why stainless is, er, stainless, it forms a microscopic layer of chromium oxide on the surface that keeps oxygen away from the iron in the steel).
I could put a slab or two of graphite in the post, a lot safer!

Dave H. (the other one)

 

[fixerupper]

I had a rotivator to restore this year the tank had been left with two stroke in it for a few years ....the tank was sound but very gunged up and rusty in side .I tried caustic and it helped a bit ...the best was a length of chain and a bit of diesel ....I left it for a day or so and every time I walked past it in the workshop I gave it a few shakes ....

 

[lchris21]

I used some soda crystals and a cheapo power supply on a "new" imported tank a few years back. Got most of it out, but I still flushed with some chemicals (cannot remember what I used?) and eventually lined it before it saw petrol..

 

[Bluemotion]

Got form on many tanks for this, have used electrolysis but I don't like it especially for odd shaped internals like bike tanks, especially if there is some previous sealant goo still attached.
Aggressive (ish) chemicals are more efficient, depending how bad to start, even to the point of needing nuts / bolts / what have you, per the OP internal tank state.
At the point there is hardly anything loose left, I go the POR15 process route but don't use their expensive proprietary chemicals. Replace stage 1 & 2 with (1) hot high strength alkaline cleaner - which is what they lable as massively expensive marine clean, (2) phosphoric diluted solution which is what they label as metal ready, equally expensive - and both stages can take a fair few goes!
What I do rate is their sealer finish, just checked a bike done in 2013 and its still looking good despite the rubbish fuels - a bendy camera stick thing is useful for this, be amazed at how cr@p & rust can still be stuck to low areas you might think are clean.

If they are Krauser panniers on that MZ they are worth more than the bike BTW

Thanks for the knowledgeable info. I just often wonder if people generally brim the tank or just part fill them with chemical strippers as the first option can become expensive to fill and harder to dispose but probably better for the stripping.

Oh a yes they are krauser panniers!! It’s one of five bikes I got free last summer!!

 

[Screwdriver]

Here's one I did earlier, Feb last year (seems like yesterday).

Dunked it in a (cold) bucket of citric acid and just left it there. About a week.

Difficult part was making sure the tank was completely full with no air trapped. That's why I don't thoroughly recommend this process, it is tricky and I kept rotating the tank over the days.

Came out ok though.

Screwd.

 

[Bluemotion]

T

Here's one I did earlier, Feb last year (seems like yesterday).

Dunked it in a (cold) bucket of citric acid and just left it there. About a week.

Difficult part was making sure the tank was completely full with no air trapped. That's why I don't thoroughly recommend this process, it is tricky and I kept rotating the tank over the days.

Came out ok though.

Screwd.

That’s cleaned up magic although you must have had about six or more gallons of the solution made up in a vat?

 

[Screwdriver]

T
That’s cleaned up magic although you must have had about six or more gallons of the solution made up in a vat?

Uh, dunno. One big bucket.

Probably had no more than a cupful of citric in there though, just enough to turn the water acidic. Then, as with electrolysis, you can use time instead of power.

 

[Bluemotion]

So, progress report.....
Yesterday I had some quality time in my work shop for a good half day making things and also cleaning my tank electrode. It got quite manic on the tank side of things as I thought it needed stripping every 30 minutes of freshly collected rust but in fact it formed far quicker more like 5-10 minutes before the electrode was thick brown with rust and wouldn’t conduct anymore!! How people say they leave it overnight to strip rust beats me as it’s so labour intensive!! Anyway,I cleaned it out and dumped the solution and still noticed small flakes and grit resembling Kellogg’s albran come out.
So today I changed my method and I’ve copied @Screwdriver s method with a vinegar solution using ‘Home Bargains’ off the shelf cheap 39p per half litre 5%acid x2 for a good measure and brimmed it air free. I’ll put that to sleep for a few days now then I’ll part empty it and throw some nasty plasterboard screws in as I find those very vicious on the hands and shake it to death.

I do appreciate all the people on here who have given useful advice btw!! Eric