Three years ago I had to cut a keyed type hitch lock off my bus to remove tow bar. The lock itsef was stainless steel but the insides were corroded. I decided to try stuffing the new lock with grease, no special grease, just what was handy. Here it is three years latter and today I put the key in the lock turned it, it opened and came right off!!!!!
HTH Jim
Nothing like real world experience. I will grease mine too!