Rusty Tank - thinking electrolysis - looking for those with personal experience

[Disco]

Please stay on topic.  I have POR-15 on the shelf.  I know about bbs and lead shot and vinegar...  I don't need suggestions for other methods UNLESS you have tried electrolysis and it did not turn out well for you.  Thank you!

The rescue I picked up last weekend will clean up nicely outside, but the inside of the tank looks bad.  It took 3-4 days of penetrating oil and some gentle persuasion just to open the gas cap.  I will remove the tank this weekend to drain it and inspect the underside, but I don't believe there are any perforations.  Have any of you used electrolysis to de-rust?

If so, what did you add to the water to make it more conductive?  Sodium Carbonate?  Sodium Bi-Carbonate?  Something else? 

I know the anode will go inside the tank and the tank itself will be the cathode.  Did you fill the tank with electrolyte and change tank positions to cover all the inside surface, or did you submerge the tank?

I have a damaged tank I can use to experiment with, but I'm hoping to shorten the learning curve by asking here.

TIA

Dave

[Large]

I have not used electrolysis for a fuel tank But I have used it for brake drums, backing plates, and several cast iron skillets, even a 9 inch ford rear carrier housing  It works good but make sure your charge is not a smart charger or it will not work I use 10-50 amps depending on how bad it is I use arm an hammer washing soda.  Fill to the top so you don't have to move tank 

[Pete]

Here is what I used, worked like a champ.
It is a little challenging to get the tank completely full due to the tank filler design.
Use a hose to evac the air or fill the last quart of fluid.
Do not submerse the tank unless you do it before applying the charger and do not apply the charger without drying the outside of the tank.



  Jason’s de-rusting method

 Hi all, I've gotten a few requests for the magical gas tank derusting
 process.  Wonder if it deserves space in the faq?

 You need
 1 rusty gas tank
 1 small container of sodium carbonate, chemical compound, Na2CO3 pool/spa supplies PH+
 1 4amp or better battery charger
 1 average bolt approx 3/8 x 1.5
 1 short length of copper wire, ~ 12 awg
 1 qt naptha
 1 qt denatured alcohol

Empty out all the gas, take out the petcock and remove the fuel cap.  Remove  any 
old fuel residue and varnish with a good rinse of naptha, make it
petroleum  free and  then drain / dry.  using a sock with a handful of small
nuts/washers etc, add a little water  and shake this  all around inside the
gas tank to loosen the big chunks, rinse with clear  water scrub well. In a
decent pail (not oil drain bucket), dissolve some of the sodium  carbonate in water,
1/3 cup for say a magna, 1/2 cup for a sabre in a gallon of clear water, 
when its dissolved  all the way stir it a bit more!

Seal up all but the filler cap opening on the top, pour in the well stirred
mix using a funnel if you've had too much coffee.  Fill the tank right to the
top with water,  set the tank so  that the cap opening is the highest part,
burp out as much air as possible  and keep the  tank full for the process.

Wrap a half dozen or so turns of the wire around the bolt to hold it  secure, 
twist it tight  so the bolt won't fall off.  Attach the (-) lead of the batt
charger to  the  outer shell of  the tank, attach the (+) to the other end
of the copper wire, suspend the  bolt in the  solution and turn on the battery
charger to a fairly high rate, an amp or  two flowing is  good, then wait.
Time to process is ~48 hours and it won't overdo itself.


The bolt gets nasty after a day, I cleaned mine now and again  to remove the
crud  but  not  sure it helps.  After a couple days, remove the leads,
discard the bolt, save the wire,   drain and rinse the tank well, drag out
that sock and slosh it all around to remove any loose material. 
Rinse a few more times until the rinse water seems clean, shake well and
then use a bit of the alcohol to fetch out the rest of the water.

Once the tank is dry, you're all set to put it back into service.
More coating not required

Science, maybe remove this junk   The process by which rust forms is
electrochemical in nature so this method employs a reverse current flow
in an alkaline bath at a higher voltage to reverse the process at a quicker
rate. There are actually two forms of rust: iron III oxide or red oxide
(Fe2O3) and iron II, III oxide or black oxide (Fe3O4)(FeO). Black oxide
is a smaller molecule. The electrolytic process converts red rust to
black rust and in the process the black rust becomes weakly bonded to
the base metal. The black rust that takes the place of the red rust can
be easily wiped, washed, or brushed off leaving rust free base metal.
Any pitting that has occurred will remain, this method will not repair damage,
but the pits will be rust free.

This is an alkali process and not acid, so you don't have a lot of pits
in the steel filled with stray hydrogen ions which would just love to start
rusting immediately instead of a much less active coating of black oxide.

 -Jason