for semi long term I use a product called mold shield made by a company called Slide. its a dry aerosol application. good for 2 yrs storage indoors. primarily used for the mold industry when storing a mold which is bare steel in most cases. works good. does require a light wipe down of WD-40 etc when youre ready to shoot it again. works very well where I live (iowa) very high humidity in the summer. I have seen this selling on fleabay if you only want a single can otherwise its sold in case quantity.