RUSTPROOF
rustproof, rustproofed
(adjective) treated against rusting
Source: WordNet® 3.1
Etymology
Adjective
rustproof (comparative more rustproof, superlative most rustproof)
Resistant to rust, oxidation and corrosion.
Synonyms: nonrusting, stainless
Verb
rustproof (third-person singular simple present rustproofs, present participle rustproofing, simple past and past participle rustproofed)
To make resistant to rust, such as by applying a coating.
We'll rustproof the metal with a good coat of paint and then we'll be able to leave it outdoors for years without damage.
Source: Wiktionary