I have an old Simair compressor which was bought brand new 20 odd years ago, but which I've only really used extensively for the past 4 years. Obviously, over the preceding 16 yrs or so, it was sat unused and I was concerned that the tank may have rusted over that time. Well, yesterday my fears were confirmed when I switched it on and heard a 'puff', after which there was a continual hissing, and, moving it to see where the hiss was coming from, I found water pooling around the base and a jet of vapour coming from a small 'chip' in the tank's paintwork. Clearly, the tank has rusted and has 'b