Fuel Tank Electrolytic Rust Removal

[Macamon]

You're welcome, Mark! Glad you found it of some use!

DOH!.. Uh.. Er... SCOTT!

Well, I dumped out the electrolite from the 2nd cleaning and the anode was just as caked on as the first was. There is still some black patches on miscellaneous parts of the tank but I'm going to have faith in the phosphoric acid to finish the job. Besides, I doubt it is enough to cause me problems. The process continues.

[3Phase]

Mac, before you use the phosphoric acid and do the final rinse, keep using the electrolysis for a while and move the electrodes around to get them out of the different different 'shadows' inside the tank. The current only flows 'line of sight' so there will be parts that were missed unless you move the anode to where it can 'see' the previously hidden areas in the tank.

Next, drain some of the electrolyte and insulate the anode from the filler neck. Flip the tank up and stand it on one end (the front) in a sink or a tub and run the electrolysis for a few more hours, then do the same with the other end (the rear) to get the rust that builds up at the very top of the tank under the filler neck.

You can shine a light in the tank and look through the petcock holes to see if the rust has been converted and cleaned off or if it is still there hanging around and waiting to plug up the fuel inlet screens <muh wah hah hah!>.

[Macamon]

Thank you for the heads up Scott, You are a little late though as I started the phosphoric bath early this morning and finished it this afternoon.
Actually it got pretty clean with a couple small shadows on the sides which I was able to slosh a wet sock around and knock it off. HOWEVER. My project was a fail anyway I went home today and dumped half a box of baking soda into the tank to neutralize the phosphoric acid, dumped that out and filled 'er back up with water and put the other half box of soda in and let that sit for a few minutes before sloshing it around and then out. I put the tank in the sun to dry and when I got back to it to check it out I looked inside to find... FLASH RUST.
I think I have some of the rust desolver from when I did the model A so I'm going to break down and use it to finish the job. This tank was easily 1/8" thick with krunk when I started and now I can see metal... Progress not perfection.

[3Phase]

FLASH RUST

Yech, 1/8" of rust? Better check for pinholes in the tank before you put fuel in that puppy. What did you use for the phosphoric acid?

I've used CLR before but when I tried it on a friends tank a while ago I found out that they, along with quite a few other companies, changed their formula to use eco-friendly citric acid instead of phosphoric acid. Citric acid cleans metal and removes rust but it doesn't create iron phosphate or prevent flash rust afterward.

So, I went to Home Depot and bought a gallon of Klean-Strip Phosphoric Prep & Etch from the paint department and that worked nicely.



MSDS for Prep & Etch

[clcorbin]

Don't get discouraged. The flash rust is to be expected. You end up plating out VERY pure, VERY small particles of iron. That stuff will rust in the time it takes you to yawn if the conditions are right.

When I did my tank back in January, I had beautiful steel inside there until I rinsed it out with hot water a couple of times. The instant that dried, it left behind that not so nice layer of flash rust you have.

My next attack on it was to hit it with hot water and some CLR (yes, the kitchen/bath cleaner). The chemicals in the CLR took care of the rust and left the tank a nice, steel color when the mixture was drained and dried out a couple of hours later.

Unfortunately, the electrolysis ALSO found a couple of pin holes in the bottom of the tank that had been sealed with rust. I bit of good epoxy tank sealer took care of that problem until I can strip the tank and give it 100% inside/outside electrolysis job and then bodywork/repair and repaint. I WAS going to take care of that this summer, but I ran out of time.

[clcorbin]

I've used CLR before but when I tried it on a friends tank a while ago I found out that they, along with quite a few other companies, changed their formula to use eco-friendly citric acid instead of phosphoric acid.

Interesting. When I bought my gallon of CLR (also from Home Depot), I checked the ingredients and it clearly lists phosphoric acid as one of the more prominent ingredients.

I wonder if they are still making both "flavors" and only sell the eco friendly stuff in areas that have banned phosphoric acid? I remember that they implements bitterant agents in antifreeze here in Albuquerque well before the requirement became national.

[3Phase]

I wonder if they are still making both "flavors" and only sell the eco friendly stuff in areas that have banned phosphoric acid?

You know, that's entirely possible. Ever since the '60s/'70s manufacturers have been cutting back or completely eliminating phosphorus in their products. I suppose it's a good thing but I wasted several hours trying to get rid of flash rust in a fuel tank until I spotted the "New Formula!" blurb on the bottle of CLR I was trying to use and found out what was really going on.

I'm still looking for TSP (Tri Sodium Phosphate) that actually has phosphorus in it instead of sodium carbonate. The new formula makes great a electrolyte for electrolysis but it just doesn't clean and degrease like the original formula.

[Macamon]

[QUOTE=3Phase;292710]Yech, 1/8" of rust? Better check for pinholes in the tank before you put fuel in that puppy. What did you use for the phosphoric acid?

[QUOTE]

I’m pretty sure the 1/8” rust was a combination of varnish, rust, and dirt (this tank still has no fuel cap) I used a TSP clone that they sell at Home Depot or Lowes
I think I’m going to look for the Klean-strip next. What were your methods of use?

[3Phase]

I think I’m going to look for the Klean-strip next. What were your methods of use?

Safety first before you even think about cracking open a gallon of 40% or 50% phosphoric acid!

Get some latex gloves and eye protection and make sure you wear them.

Always add acid to water.

Don't scratch your nose and don't bite your fingernails.

Buy a couple of extra boxes of baking soda, TSP or washing soda to neutralize the acid in case the bottle gets spilled or the tank dropped. It can take a lot of water and a lot of neutralizer so work outdoors if you can.


The Tank:

Add about two cups of phosphoric acid to five gallons of cool water and mix them together. There really aren't many five-gallon plastic buckets that are easy to handle so add one cup of acid to a two or three gallon plastic bucket of cool water, empty it into the tank, then do it again until the tank is filled.

Let the tank sit for about an hour then drain it and rinse it with water and baking soda (or leftover electrolyte from the electrolysis stage if you're done zapping gas tanks for a while) to neutralize the acid in the tank.

Flush the tank with cold water then let it drain.

Put the tank on some rags or newspaper and raise the front of the tank with a wooden block. Put a shop vac hose in the tank's filler neck, put a rag around the hose and let the vacuum pull air in through the petcock holes until the tank is dry.

You should now have a clean, dry, tank with a light coat of iron phosphate inside. It won't last forever so keep the tank dry until you are ready to fill it with fuel!

[clcorbin]

Put a shop vac hose in the tank's filler neck, put a rag around the hose and let the vacuum pull air in through the petcock holes until the tank is dry

I completely forgot to mention that! In the dry air here in Albuquerque in January, the tank was dry in less than 10 minutes.

[3Phase]

I completely forgot to mention that! In the dry air here in Albuquerque in January, the tank was dry in less than 10 minutes.

Heh, yeah, out in the desert the water's already almost completely dry when it comes out of the faucet anyway!

If you're not going to use the tank right away and you're not living in the desert with -75% humidity: put some ATF in the tank and shake it around until it coats the inside of the tank to slow down the rust. Don't forget to clean the ATF out of the tank with mineral spirits before using the tank again.

[62xs]

I use metal wash I got from Eastwood. When you sand blast a part for powder coating you spray it on and it stops flash rust.

I also use it when I dip my parts and electrical connections in rust dissolver.
After i wash them with soapy water.
Then I put oxy guard in the connectors so they don't oxidize again. Oxy is used in home electric boxes to prevent oxidation.

[jetmechmarty]

Metal rescue

I saw this stuff demonstrated on TV. It was on TWO GUY'S GARAGE. It looked like the answer to some of these problem. It's called Metal Rescue. I don't know what's in it or how it works. Have any of you tried it? See the link.

METAL RESCUE

[3Phase]

Marty, 62xs:

I've been looking at the scanty MSDS for Eastwood's Metal Wash and Armour's Metal Rescue. There's not much online but they appear to have various forms of sodium silicate and some phosphates to remove dirt, oil, grease and rust and leave a thin coating on bare metal that prevents further rust for a short period of time.

Yamaha's own fuel tank cleaning kit uses them both in a two-step process: a phosphoric acid and water soak followed by a sodium metasilicate rinse to neutralize the acid and prevent flash rust. A gallon of ~40% phosphoric acid from Home Depot is a lot less expensive than a gallon of Metal Wash or Metal Rescue and pounds of powdered sodium metasilicate are pretty cheap, too.

Electrolysis will revert as much rust as possible back to good iron and steel. Following up the electrolysis with chemical cleaning should dissolve any remaining iron oxide that was missed and the magnetite left in the tank after electrolysis. The phosphor and/or silica compound coatings will help prevent flash rust.

The silicates and phosphoric acid both form protective coatings on exposed steel and iron but the silicates are marginally more eco-friendly and appear to be favored for drinking water systems. They prevent rust in cast iron pipes and minimize the amount of lead dissolved in the water from old solder joints without making huge algae blooms in the holding ponds. No one likes drinking water full of algae or red water full of rust!

[clcorbin]

Nice info Scott.