I can't believe Bill Stevens hasn't jumped all over this. He's the "metal guru" and he recently sent me down a research path that was a real eye-opener. I don't question the fact that many have had great success with Sharpies, but here's what happens (and yes, Mr Stevens, feel free to jump in a tell me how perfectly I explained this);)
Stainless steel does not corride because of a passive layer of vapor called Chrome-Oxide that hovers on the surface and protects the metal (sounds crazy I know, but that's how it works). When the metal is scratched or ground, the vapor reforms to once again protect the surface, but now, there are tiny microscopic ridges and valleys where bad things can hide. They breach the vapor barrier and begin to corrode the surface (this, by the way, is why the grade of stainless is actually not as critical in corrosion resistance as the polish. 304 can match the performance of 316 if it is polished to an optimum level). One of the most corrosive agents to stainless is CHLORIDE. Stainless doesn't turn orange when it corrodes so you're not always aware of whats going on, but one of the key ingredients in marker ink is CHLORIDE. In fact, in the metal industry, markers containing chloride are BANNED FROM USE and can't be used to mark or note any kind of stainless steel. The industry even sells low chloride markers specifically for stainless steel [
www.nissenmarkers.com] . We recommend the use of approved Low Chloride Metal Markers or paint for re-coloring ground black feet. We also suggest using a finer grit stone to maintain as much surface shine as possible. By the way, Stainless Steel does not turn orange when it corrodes. If you have orange stainless, you (or someone else) has introduced iron of some sort to the surface i.e. a metal file to grind the foot. The use of a stone grinder should reduce or eliminate this problem.
