Flash Rust problems

[DucatiGuy]

Hey guys,

I had some tank rust in a bike I just bought so I let it sit in apple cider vinegar over the weekend. Went to remove the vinegar and clean with hot water, and I noticed a lot of surface rust showed up minutes after. I had a little vinegar left so I put it in, rust went away, and then came back after using water to rinse.

Is there something better than water to use?

[Petorius]

No experience with this, but I would try bombing it with WD40 right after the water rinse.

[Tekime]

I haven't done a metal tank but I think phosphoric acid is what you're looking for, directly after washing. Worth a Google.

I've de-rusted a ton of metal bits from pedal and motor bikes and I usually wash with warm water after de-rusting then immediately dry them and drop them in some motor oil, otherwise the moisture rusts very quickly. Not sure dumping motor oil in the gas tank would be a good idea though... unless it's a 2 stroke?

[NPDCPA]

Get a POR-15 kit, coat the inside and call it a day. It requires a light surface rust for adhesion.

Coincidentally I have 2 tank kits but only need one if you're interested.

[klp]

No need for the real kits, I have used white vinegar on plenty of tanks.

Like petorius said you have got to coat it right away. I dump the vinegar and rinse for a while with the hose. If you use a strong stream you can blast out any loose bits that remain. As soon as that's done I shake out out much water as possible then blast it with your favorite cheap oil.

Do this next part at your own risk but I set up a hair dryer to blow in the fuel inlet and leave it there for a while. Once the tank is completely dry I take some 2t oil and roll it around as best you can. This has worked well for me on many tanks, even well rusted out ones. Most recently I had a tank in real rough shape but leaving the vinegar in there for 3 days did the trick.

Remember to remove the fuel tap and make a plug of some sort. Best results if you get rid of excess oil and put fuel in it ASAP. The more fuel you keep in there the better.

[Kurlon]

Use Evaporust or similar instead of vinegar. The coating it leaves behind will continue to prevent rust while you wait to decide what you're going to do to the tank.

[NPDCPA]

Tank sealing kits prevent future rust. One and done.