Materials: Stainless Steel 304 (indoor use, not resistant to marine conditions ) and PMMA. Stainless steel gets the "stainless" portion of its name from its chromium oxide coating that resists staining, pitting and rusting. But although it holds up better than other metals, stainless steel is not impervious to rust. Time and certain environmental conditions like salt air will slowly erode stainless steel's protective coating. When the chloride in the aerosolized salt in salt air lands on the surface of the stainless steel, it breaks down the chromium oxide.