Judging by the name, you could assume that stainless steel never rusts — but you would be wrong.
Stainless steel oxidizes less easily than other iron-based metals, but is not literally "stainless." Like standard steel, stainless steel can be marked with fingerprints and grease, develop discoloration and eventually corrode. The difference is the resistance. Stainless steel can withstand much longer and abuse before showing signs of wear.
All steels have the same basic iron and carbon composition, but stainless steel also contains a good dose of chromium-alloy that gives stainless steel its famous corrosion resistance.
And this is where things get complicated. There are multiple grades under the shade of stainless steel, each with a slightly different alloy composition, and therefore slightly different physical characteristics.
Stainless steel must contain at least 10.5 percent chromium. Depending on the grade, it may contain much higher levels of chromium and additional alloy ingredients such as molybdenum, nickel, titanium, aluminum, copper, nitrogen, phosphorus and selenium.
The most common grades of stainless steel are 304 and 316. The key difference is the addition of molybdenum, an alloy that dramatically improves corrosion resistance, especially for more saline or chloride exposed environments. 316 stainless steel contains molybdenum, but 304 does not.
For exterior fittings such as rails and bollards, stainless steel is an ideal corrosion resistant material, but will only withstand long-term exposure if the grade is appropriate for the environment. 304 is a more economical and practical choice for most environments, but it does not have the chloride resistance of 316. The slightly higher price of 316 is worth it in areas with chloride exposure, especially on the coast and roads strongly Salted Each application for stainless steel has its own unique demand.