If its galvanized it shouldnt rust for a while. Wire fences are usually galvanized, and you dont see very many rusty ones. You don't see it used in food applications very often. I remember in high school metal shop teach told me not to weld on galvanized steel because it would emit toxic fumes. I think you would be fine taking your time, maybe eventually replacing with stainless. But, if its not touching the wort, probably don't have to.