Glossary

304 is the most versatile and the most widely used of all stainless steels.  Its chemical composition, mechanical properties, weldability and corrosion/oxidation resistance provide the best all-round performance stainless steel at relatively low cost.  It also has excellent low temperature properties and responds well to hardening by cold working.

Carbon = C
Mn = Manganese
P = Phosphorus
S=Sulfur
Si= Silicone
C=Chromium
Ni =Nickel

300 series stainless steels make up over 70% of total stainless steel production. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures to the melting point of the alloy.

316 Stainless is differentiated from 304 by the addition of addition of molybdenum and a slightly higher nickel content.
The resultant composition of  316 gives the steel much increased corrosion resistance in many aggressive environments.  The molybdenum makes the steel more resistant to pitting and crevice corrosion in chloride-contaminated media, sea water and acetic acid vapors.   The lower rate of general corrosion in mildly corrosive environments gives the steel good atmospheric corrosion resistance in polluted marine atmospheres. 

Low carbon 316, know as 316L is made with the same compounds and reduced Carbon. The reduced carbon further reduces the risk of corrosion.

Carbon = C
Mn = Manganese
P = Phosphorus
S=Sulfur
Si= Silicone
C=Chromium
Ni =Nickel
Mo=Molybdenum