To clean the canister from rust there are many different ways, here are some of the most effective.
Method the first. Take the canister and wash it using washing powder machine (the one that is intended for use in washing machines). Please note that if you use powder for hand washing, it may be too much foaming, and time-consuming process of leaching the foam from the canister.
Then take phosphoric acid and also treat canister. You can also use a weak solution of sulfuric-acid battery, but in this case, strictly follow the process, as the acid along with rust can eat the metal itself, purified of its surface requires special protection, or very quickly re-covered with rust.
The second way. Use hydrochloric acid inhibited with hexamine (whisper of dry powdered fuel), also try formaldehyde (also called formalin). This method allows to spare the metal, but at the same time will remove the rust. After all the manipulations with chemicals, rinse the canister with water. For additional protection from future rust, use a solution of phosphoric acid, in the end you get a dense layer of iron phosphate.
The third way. Pour into the canister at night a weak solution of citric acid (sold in any store). Dilute acid in a ratio of one gold bag with 20 liters of normal water. Once done, rinse the canister with water and dry (for this purpose better use compressed air). To ensure the canister further protection, use epoxy resin with a hardener. Just screwed it in kanetsu, shake well and pour out the excess.
The way the fourth. I say that with the rust copes regular Coca-Cola. Mix 4 liters of coke and citric acid and pour the composition in the canister. After that, pour half an hour a weak solution of reasonablerates.