Hello friends I am four stroke enthusiast but one year ago I successfully finished two cylinder steam engine. I run engine on live steam roughly 30 minutes then I had to turn to different project so I put engine on the shelf . Last weekend I had spare time so I decided to check steam engine and I have found out black spots on inner liner surface. These spots are probably corroded but they are dark black not rusty red. I machined liners from unknown ferrous material . Steam gurus my question is : What should by done before steam engine is stored. Should I run engine on compressed air to remove all condensed water from engine or you have a different remedy. Thank you very much for your help.