Rust on the lower engine part

SouthArk370Z

I've never used or even heard of Rustol. Did a web search and most of the pages were in French, which I cannot understand.
I've used a lot of different CRC products through the years and have always been very satisfied with their performance. If you can find CRC products in your area, it will be worth the effort. Another company that makes good rust-control coatings is Rustoleum.

I'm not sure what that part is. If it's solid bars, then it will be OK to sand, buff, blast, etc. If it is tubing, you run the risk of poking a hole in it when you clean it.

Rust can be rather abrasive and may have caused some excess wear of the belt - a good inspection will tell you if you need to replace. It doesn't look like it needs to be replaced in the pictures.
The pulleys just need a good cleaning/coating. Do not paint where the belt rides - the belt will abrade any rust in that area.

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