I've been making some French screen doors. Each inactive door will have two flush (recessed) bolts in the door edge, one at top, the other at the bottom.
The slide on the bolts is held at the open/closed positions by a detent/socket in the bolt and it's case. The bolt is kept from sliding out of the detent by a small piece of bent spring steel.
The bolt and case are made of non rusting material but the spring isn't. Before installing in the door I want to pack something into the bolt case around the spring to retard rusting. My question is, what would be most long lasting? Axle grease? Lithium grease? Vaseline? Paste wax? Other?