I've used those erasers for years they're great for rust. Be careful on a folder, and try to avoid getting it down into the moving parts. It does have abrasive material in it that could cause extra wear on moving parts if not removed. So my advise is carefully erase with the blade pointed down, making sure to wipe any residue off thoroughly, then wipe it down with Tuf-Cloth to help prevent and protect it from future rust.

I can't believe S30V would rust that easy... <img src="/ubbthreads/images/graemlins/ooo.gif" alt="" />

I EDC a small fixed blade made of 1095 everyday and rarely have rust issues even with it... <img src="/ubbthreads/images/graemlins/crossfingers.gif" alt="" />