using a fire extinguisher as a boiler

[markieb]

hi guys is there a specific way to clean up a fire extinguisher tank?
the one i have i believe is stainless steel they were thrwing it out at work so i commondeared it from the skip.
its a red tank with water written on it theres no leaks and the inside seems clean,but ive heard some of these types of tanks have a thin ldpe lining and was wondering how to clean this plastic lining out of this really handy little spirit run tank its a 9 litre tank so would be ideal.should i use an acid of some sort or just throw it on a fire and burn it out?this little tank will be excellent ive got the compression fittings already for it and have a decent sized length of copper to use for the top and it frees up my keg then and could posssibly have a extension set up so i could run my batches straight from keg take off the foreshots and heads through the first liebeg arm then open a valve and allow to run straight into the extinguisher and spirit run it if it could handle the slow fill speed.
whats your thoughts on this and any help especially on the extinguisher clean up.
many thanks