On the contrary to some who stated stainless steel rusts...
Yes some stainless steels rust, some much worse than others, however some DO NOT rust at all! There are at least 50 types of stainless steel alloys. Some created for holding a knife edge, heat resistance, easily weldable, springyness, RUSTPROOF, tensile strength, etc.
And easy determination, would be to take a magnet with you and see if there is an attraction to the part, if there is a strong attraction, there will be a likelyhood that the part will rust, but its not a 100% test, with experience you can determine the strenght of attraction of the part to the magnet.
The 300 SS family, the best are 304 and 316, many fasterers found at Home Depot are 304 or something very close to that alloy. "Fastenal" has both 316 and 304 fasteners, 316 fasteners are always stamped as to their quality "316 SS". 304 will rust to some degree in salt spray, it will discolor, with very light pitting, removable with a sandblaster(difficult to use sand paper), to make it look like new. 316 would be my choice for hood pins since ocean air/spray is rather salty and will corrode 304 to some degree. Torsion pins can be made out of a non-rusting stainless steel as well and still be springy but will have a slight magnetic attractance, likey made from 302SS.
Its consumer fraud that parts manufacturers says stainless steel when its not. But unless you have access to a gas chromatography spectograph machine, might be difficult to prove your case, unless the part is so badly rusted and pitted(most stainless won't pit deep if it does rust).