yeah but was it new used oil? If it was used it was likley too acidic. If it was new then there should not have been a problem except for the action of keeoping the engine submerged in the oil.
As I said, too acidic an environment or too basic an environment can have the same effect. All thats needed is a coating of oil so the polar anto corrosion additives can get into the bits they need to.

Simple, no need to reinvent the wheel here.