I have been in Texas for 12 years, before that I lived in the Detroit area, the rustbelt of the USA. Rust is a cancer to metal. In my experience, there's not a lot you can do to remove the rust that will keep it gone forever. It sounds like you have the original metal roof and some screws that are rusting and rubber washers that have broken down. A broken washer can cause some roof leaks, but they would be minor. If the metal around the screws looks bubbled or blistered, that would be the start of rust. In my experience the best way to deal with rust is to cut it out and put down new metal. The new metal that is put down needs to be coated/painted on both sides. Where the new metal overlaps the old metal make a seal around it with caulking to ensure it's water tight. If you use unpainted metal, it will rust. If the bottom is not painted but the top is, the bottom will rust. I have been successful with rust repairs where I used galvalume metal sheets or other colored metal sheets. What I have seen that rusts out is when metal sheets from the hardware store were used for patches.
Keep in mind your proximity to the Gulf and the salty air.
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Justin Vosburg
Property & Equipment Supervisor
Affordable Attic Self Storage
Harlingen TX
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