We have a little beach hut, and everything metal is oxidizing like crazy because of the salt water atmosphere. The electrical installation is very "artisan", so to speak.

I've noticed that the lights dim way more than they used to do a couple of months ago when we use high amperage appliances.

I suspect that some of the connections have oxidized quite a bit, and may be the source of these voltage drops.

How can I isolate the cause? Would it be as simple as measuring resistance? How many ohms could I expect to see on a slightly oxidized or lose connection?

Also: does "contact cleaner" spray help in those cases? Is there some product (maybe a conductive spray or gel) that I could apply to contacts so that they don't oxidize as quickly?