[Superman]

Well.....engines parts can be protectively coated and I suppose the coatings can be effective and last a "long" time ("long" being undefined here). But then there are the electrical parts and the generator/alternator windings are going to be exposed. We know these manufacturing preparations can protect for a time, but we also know that time is not forever. A question of when, I suppose. Worst case scenario....you run them every six months for several minutes or so. Or perhaps once per year, and fog the engine before storage.