Hodaka tank repair,

[MTrat]

It seems there are many approaches to 'derusting' and treating an old tank. I have tried a few myself. What are some preferred methods? Perhaps this is a good 'Resonator' topic,

[viclioce]

I use Muriatic Acid diluted 1:4. Works quickly in most cases. I use a gallon of baking soda water to neutralize afterward. Then I rinse and air dry with my compressor and coat with a 50/50 mix of 2 stroke oil & fuel. Danny Cook taught me to use this method. Victor

[Dale]

I think I have tried every method documented out there. Electrolysis, vinegar/salt solutions, muriatic acid, oxalic acid, Evaporust and have found that the easiest method is also the most effective. It is safe and by far the cheapest.

This method is thorough, it will not harm the external chrome (rinse off painted surfaces) and it etches the metal so that flash rusting is not an issue. The product that I use is Rustoleum Rust Dissolver Gel ($9.95 at Home Depot in the paint dept). Also available as Krud Kutter Must For Rust Gel if you can find it. These are Phosphoric acid products.

Step 1.
Flush the tank with warm water and Dawn dish soap. Rinse with water and drain. No need to dry it as the rust remover works best on moist metal.

Step 2.
Prepare a surface where you can place the tank in various positions safely. A large rubber tub works great. Temperature is critical too. Work in an area where it is above 70 degrees.

Step 3.
Remove the petcock and seal the opening. Cork, rubber plug, tape, etc... Then pour half the bottle of rust remover gel into the tank followed by a handful of drywall screws. Place some plastic wrap over the fuel cap opening and install the fuel cap over that. Now shake the tank to coat the entire inside. Set the tank down and set a timer for 30 minutes. Every 30 minutes shake the tank and rotate it. After all four sides plus the two ends have been treated, shake, shake and shake some more. Dump your solution then rinse with warm water with Dawn dish soap followed by clean water. Air dry and add oil. I like to spray it down with fogging oil and later flush with a little premix.

The time for treatment varies for the amount of rust you are trying to remove. Small amounts require maybe 15 minutes per rotation and larger amounts might take 30 minutes or more and might require several treatments. Just don't let the gel sit in one place until it starts to dry on the surface. It must stay wet.

[matt glascock]

I would add one bit for those following the thread. Before proceeding with de-rusting, consider a few aspects of the tank first. How severe is the rust? Are there patches of rust over bare metal or is the entire tank lined with bristling rust and crust. If you successfully de-rust the option b tank, you may be left with a watering can's worth of pin holes rusted through. There's personal experience backing that statement. If the tank is severely rusted on the inside and any rust on the chrome, you might be facing the same dilemma. Fear not. Caswell 2-part epoxy resin tank sealer works excellently in this situation - actually the more rust and crust the better. The only prep necessary is a couple swishes with acetone and sheet metal screws to knock off and loose rust and flush and oil residue. Follow the instructions with the epoxy kit precisely as you would if you were assembling a home built rocket kit intended to take you into near-earth orbit and return you safely to terra firma. Prep and application instructions included. I have four tanks in regular service, including an alloy tank on a TM-125, treated thusly and all function perfectly.

[Dale]

Spot on Matt...

[gregg_floren]

I've been a big fan of Evaporust. It works well and it's safe. You can store it and reuse it. You can use it inside with minimal ventilation and it won't ruin your clothes or burn your skin.

However, I've wondered if, after removing any loose rust flakes from a tank, would it be better to use a product like Ospho or Locktite Rust Converter? These products convert the remaining rust to iron. Seems like maybe that would reduce the occurrence of pinholes/leaks after de-rusting and actually strengthen the tank rather than possibly weaken it by removing material

Like a lot of things, I've just thought about this but never actually tried it.

You could still use a tank lining product afterwards if necessary.