I have a cast aluminum screw-in deckplate that was seized up solid. At least for the half dozen years I've had the boat, maybe for decades before. I removed the entire thing, brought it home, and after subjecting it to various forms of abuse managed to free it up so that I could unscrew it from the mounting ring.
My question now is "what do people prefer to keep aluminium threads from seizing?"
It may turn out that it now behaves fine, especially if I unscrew it from time to time, but I'm curious. I'm reluctant to use any kind of grease, since it will liquify and drip into the boat when it's at all hot out. Spray-on Teflon? Never Seize? Nothing 'cause it will be fine now that it's cleaned up?
I note also that it had no O-ring, and when it does there should be no longer be any need to tighten it down beyond the point of compression. It may be that this alone makes all the difference.
TIA
Mickey