This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. Incapable of rusting.

adj. Resistant to rust, oxidation and corrosion.

v. To make resistant to rust, such as by applying a coating.

adj. treated against rusting

"Underneath the wicker weave, aluminum framing provides rustproof stability and strength."

rustless   

aloof    goof    hoof    poof    proof    roof    spoof    woof