Solar PV, air heat pumps and salt spray

AFAIK the metal parts on the panels and mounting system are made from aluminium, so they won't corrode

The wiring uses MC4 connections which should be weatherproof

Having said that I've heard of a couple of times that someone lost a string because the seal on a connector went

You'll probably end up with the panels covered in salt residue a lot, so you'll probably want to ensure your panels are somewhere you can get them cleaned easily enough

For a heat pump you should check the manufacturers guidelines. I remember one brand recommended to put a short wall in front of the heat pump to stop seawater getting blown into the fan assembly

If possible you should try to put the heat pump into a sheltered location