Topic: AMAZING Gas Tank Rust Removal Trick!

[736cc]

  I recently acquired a 1972 CB750 K2 w/ a perfect original paint gas tank, but the inside of the tank was solid heavy rust. Tried the usual agitating w/ a pile of nuts and bolts, then with WD40 but it still was really cruddy. I tried flushing a few times with degreaser then ran a tank of gas on the bike and ended up w/ a clogged petcock. So I tried the electrolysis technique for the 1st time and got AMAZING results! Here's what I did:
   NOTE: Toxic fumes occur during this process, so do it outdoors!
   Fill a plastic pail w/ hot water and add a container of table salt (bulk container comes in a typical $.99 cardboard cylinder). Mix well then dump into rusty gas tank. Topped-off gas tank w/ water from a garden hose. Plastic funnel in the filler neck. 12volt battery charger on 10amps. Negative to bare metal on tank. Positive clamp attaches to a valve spring and into the funnel submerged in the salty water. (IMPORTANT: DO NOT allow positive clamp or valve spring to touch any metal parts of the gas tank! The plastic funnel insulates the valve spring and positive clamp).
  Turn on battery charger, and water will percolate. You want 5 to 8 amps on the charger gauge, more salt brings the reading up.
Rust will bubble out of the tank in a steady stream (doesn't hurt paint). Tap the bottom of gas tank once in a while to loosen things up. 3 hours later, and a couple rinses w/ a degreaser, my tank was clean as a whistle. Dry it completely by rinsing w/ a bottle of rubbing alcohol.

[Old Scrambler]

I like the spring idea.........going to attempt this on a few of my 'spare tanks'

[hatchb4ck]

That is a great idea.  Thanks for sharing your process and results.  I've got a couple of tanks that will need some rust removal.

[dusterdude]

I used the works toilet cleaner on my sportster tank,worked like a charm

[Stev-o]

Have a rusty one I should try this on

[Scott S]

 I've used this method before but not with salt. It used washing soda or something? Can't remember right now.

 I've had great luck with The Works method, too. But not on super-duper rusty tanks.

[Tews19]

Can you post inside pics?

[FunJimmy]

Great tip.
I'd be interested in an inside shot too.

[singedebile]

I'm curious did you end up coating the tank anyway? or was it so clean you didnt feel the need to?

[pmurph1x]

I've tried this with washing soda (1tbs per gallon) and about a foot of rebar. the results were disappointing. It cleaned the rust off some of the tank very well ( the area around the filler cap)but it left a lot of rust in pits towards the back of the tank. This was after 4 days and alternating the rebar from one side of the tank to the other.
   I'll have to try salt - maybe that works better.

Paul

[736cc]

Pics of the inside will have to wait because right now the tank is winterized and full of gas, marine stabilizer plus a couple ounces of 2 stroke oil. The transformation from solid rust to clean metal is remarkable. Getting rid of the unending loose grit which kept clogging the petcock made my day, rust just bubbled and floated out as really gross gritty fluids during the process. Tapping the underside w/ a hammer and directing the hose nozzle at full force into the neck speeded-up the process. I wouldn't describe the inside as brand-new, there's still dark spots, pit marks, areas that are grey and not shiny, but its CLEAN and the level of improvement is AMAZING.

[greenjeans]

So...   what was the ratio of salt to water -   5 gallons water, how much salt

I've used washing powder before - it worked but took forever.

[736cc]

I used 30 oz of Morton salt in a stock CB750 tank filled to overflow. That gave a reading of 6 amps on my battery charger. I experimented w/ some junk iron to fit in the funnel and got much lower amp reading and salt ratio unchanged. I believe the valve spring conducted best so there's something to be said about that. A couple times I paused the process to flush the tank with a full pressure nozzle on the garden hose (great gobs of yuk disgourged) and I threw in some more salt and water as I resumed the electrical hydrolysis process. I think the rust was drawn to the valve spring and simply overflowed out the neck in the froth. Water was added when tank couldn't overflow, like every 15-20 minutes or so.
  It only took 3 or so hours. If I left it longer it probably woulda came out even cleaner but I was satisfied to what transformed.

[lucky]

Be careful to not smoke around the tank!!!
 Hydrogen gas gets produced with this method.

[Tews19]

[/quote]

Bike looks sick!

[donny]

 Back when this wuz new they guys prefered Borax.  Worked Okay for me.  Some of the "pros" put in a hand full of sheetrock nails and stuff in in the dryer, fluff only.
 Works great.

[Vinhead1957]

I am currently soaking my tank with a safe liquid Evapo Rust. I did use sheet rock screws to loosen the rust . My only problem is I have one gal in there and I have to migrate it to different areas in the tank. It is a long soaking process but the results so far are spotless

[dodieninja]

can you l;eave the petcock on while doing this???

[Vinhead1957]

You could with Evapo rust

[6adan]

Insted of nails I use some chain with a string on it . It is easier to get out than the nails.

[phil71]

You have to take the petcock off. That metal will not take well to thi process. I've done this a few times, and I usually fabricate a block off plate of sheet metal, with a cut inner tube as a gasket. The petcock bolt holes also make a great grounding point for the neg electrode. One thing I'm curious about, I've tried iron, and it seems to work well.. The rebar gets slowly 'eaten', and from my understanding, it's re-plating the tank as it 'donates' its molecules . The spring, while dirty, and probably more conductive, doesn't seem to have given up anything..
I also have found that a battery charger alone does not work very well. Most battery chargers still have some AC ripple in them. I use a charger with a battery inline. This stablizes the DC current AND can supply more amperage, which may help when using a less-conductive metal.

[lostinthe202]

You have to take the petcock off. That metal will not take well to thi process. I've done this a few times, and I usually fabricate a block off plate of sheet metal, with a cut inner tube as a gasket. The petcock bolt holes also make a great grounding point for the neg electrode. One thing I'm curious about, I've tried iron, and it seems to work well.. The rebar gets slowly 'eaten', and from my understanding, it's re-plating the tank as it 'donates' its molecules . The spring, while dirty, and probably more conductive, doesn't seem to have given up anything..
I also have found that a battery charger alone does not work very well. Most battery chargers still have some AC ripple in them. I use a charger with a battery inline. This stablizes the DC current AND can supply more amperage, which may help when using a less-conductive metal.

Nice addition, what type/size of battery?

How has everyone's (who's done this) experience with flash rust been?  How 'bout holes developing in the tanks since this is consuming metal?

[luap]

Tried this last night. used a 12v 10amp charger. I tied 2 valves springs together after about a hr one spring was gone
so I switched to a piece of  1' round tube used the funnel on both. after a hr again or so pulled out the tube an it was almost eaten all the way. Tank def is getting cleaner going to do it a couple more times today switch out with clean water after each hours.

[Harsh]

I am going to give this a shot in the near future.  Unless there is a reason not to, I have some old forks springs I will cut down in length and use.

[HondaMan]

I've also done this method with nails (instead of the spring), which were cheap (like me!). It worked, but took about 30 hours total time, and 3 nails.

After it was done, I applied the POR-15 kit. Excellent results!