Posted 19 March 2018 - 16:12
There are multiple different sorts of stainless steel. Some start rusting the moment container of water wanders past, others will withstand the sea (especially useful on boats...).
Were you to have a pen with parts made of marine grade S/S, and you used pH neutral inks, and there were no other metals in the ink path (except for the nib, which is usually electrically isolated from the rest of the pen), then you should have no problems.
OTOH, it's going to be pretty heavy.
I ran into this a few years ago when I was looking for food-grade stainless steel wire for a project. I went to a place that sold metal sheeting and wire and asked and they were like "No idea..." So I went to a restaurant supply and said "Is x type of stainless steel wire safe to be used around food?" And they didn't know either, but looked through various catalogs for me. And the stuff I was considering turned out to be the same type of steel as what is used for steam table trays, as it happened. So I went back to the metal sales place and said "Yes, this is what I need." They asked "How much of it do you need?" and I said, "About five feet...." And they handed it to me and basically said, "Go. Just. Go...."
Ruth Morrisson aka inkstainedruth
"It's very nice, but frankly, when I signed that list for a P-51, what I had in mind was a fountain pen."