I wonder why is sapphire corrosion resistence? Which property helps to determine that this material is corrosion resistant?
Corrosion is mechano-chemical damage of material. Sapphire is really enough resistent to corrosion, because he has very strong chemical bonds in structure Al2O3 - alpha modification. For example, Sapphire enough resistence in melt of Na by 1200K: his mass is decreasing on 1% only.