The phrases "rusty car" and "rusty tools" are more common than "rusted car" and "rusted tools." Here is a Google N-gram frequency chart. https://books.google.com/ngrams/graph?content=rusty+tools%2Crusted+tools%2C+rusty+car%2C+rusted+car&year_start=1800&year_end=2008&corpus=18&smoothing=3&share=&direct_url=t1%3B%2Crusty%20tools%3B%2Cc0%3B.t1%3B%2Crusted%20tools%3B%2Cc0%3B.t1%3B%2Crusty%20car%3B%2Cc0%3B.t1%3B%2Crusted%20car%3B%2Cc0

I would personally use them interchangeably. In your two example sentences rusty and rusted work equally well. The only time when I can think that this would not be the case would be if you were using rusted as the past participle. For example, you can say “the car had rusted by the time I bought it” but you couldn’t say “the car had rusty by the time I bought it.”