What is the difference between 304 and 316? Stainless Steels
Alloy 304 is perhaps the most widely used (austenitic) stainless steel, based upon 18% chromium and 8% nickel additions. In comparison, Alloy 316 contains 16% chromium, 10% nickel and 2% molybdenum. The addition of molybdenum greatly improves the pitting corrosion resistance of Alloy 316, albeit at an additional cost.
The most common form of corrosion in stainless steels is pitting corrosion. The Pitting Resistance Equivalent Number (PREN) gives an indication of resistance to pitting corrosion based upon the alloys composition, where PREN = %Cr + 3.3 %Mo + 16 % N. Therefore the PREN for Alloy 316 can be 4-5 points higher than Alloy 304.