304L grade with 0.030% maximum carbon is similar to the 304 grade, but with much enhanced performance in the sensitization range. Due to its superior resistance to intergranular corrosion following stress relieving or welding, Type 304L is broader in application versatility. The extra-low carbon 304L is required when welding joins heavy sections or an aggressive corrosion environment exists and post-weld annealing is not possible. 304L will become sensitized if exposed for long periods of exposure to service temperatures of 800°-1600°F. Type 304L is used where welding is required but the carbide precipitation tendency of Type 304 will impair that alloys corrosion resistance.
304 is suitable for use in a variety of applications, in fact it is the most common stainless steel, and about 60% of all stainless steel used in the world is grade 304.
Strictly speaking, stainless doesn’t rust, but like all materials, there are some environments which are just too corrosive and it will be attacked. When stainless is attacked, the corrosion product looks just like the rust you get on carbon steel.
The corrosion resistance of stainless steels mostly depends on their content of the alloying elements chromium and molybdenum, plus a few other factors, depending on the specific application. The surface finish and fabrication practice can have a major effect.
300 series austenitic stainless steels are non-magnetic. When nickel is added to stainless steel in sufficient amounts, the crystal structure changes to “austenite.” The basic composition of 300 series austenitic stainless steels is 18% chromium and 8% nickel. This enhances their corrosion resistance and modifies the structure from ferritic to austenitic. Austenitic grades are the most commonly used stainless steels, accounting for more than 70% of production.