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
Stainless steel Hydrochloric acid will damage any kind of stainless steel, and should be avoided. All types of stainless steel resist attack from phosphoric acid and nitric acid at room temperature. At high concentration and elevated temperature attack will occur and higher alloy stainless steels are required. In general, organic acids are less corrosive than mineral acids such as hydrochloric and sulfuric acid. As the molecular weight of organic acids increase their corrosivity decreases. Formic acid has the lowest molecular weight and is a strong acid. Type 304 can be used with formic acid though it will tend to discolor the solution.