SAE 304 stainless steel optimal high temperature strength. The carbon content of 304L (UNS 30403) is restricted to a maximum of 0.03%, which prevents sensitization during welding. Sensitization is the formation of chromium carbides along grain boundaries when a stainless steel is exposed to temperatures in the range of ~–. The subsequent formation of chromium carbide results in reduced corrosion resistance along the grain boundary leaving the stainless steel susceptible to unanticipated corrosion in an environment where 304 would be expected to be corrosion resistant. This grain boundary corrosive attack is known as intergranular corrosion. The carbon content of 304 (UNS 30400) is restricted
Austenitic stainless steel corrosion). The higher nitrogen addition in 200 series gives them higher mechanical strength than 300 series. Other notable austenitic stainless steels are Type 309 and 310, which are utilized in high temperature applications greater than 800°C. Alloy 20 (Carpenter 20) is an austenitic stainless steel possessing excellent resistance to hot sulfuric acid and many other aggressive environments which would readily attack type 316 stainless. This alloy exhibits superior resistance to stress-corrosion cracking in boiling 20–40% sulfuric acid. Alloy 20 has excellent mechanical properties and the presence of niobium in the alloy minimizes the precipitation of carbides during welding. Austenitic stainless