Rustier is an adjective that often describes something old, worn out, and covered with rust. If you're looking for some synonyms to describe a similar condition, then you can use words like corroded, oxidized, decayed, antique, weathered, aged, or eroded. These synonyms convey the idea that an object or surface has undergone some form of chemical or physical alteration. Furthermore, they may imply that something has acquired an attractive patina or weathered appearance that adds character to its appearance. Whatever the case may be, these synonyms enable you to describe rustier things with more specificity and nuance.