316 is an improved version of 304 due to the addition of molybdenum and a slightly higher nickel content. The resultant composition of 316 gives the steel improved corrosion resistance in many aggressive environments. The molybdenum makes the steel more resistant to pitting and crevice corrosion in chloride-contaminated media, seawater and to acetic acid vapours. The lower rate of general corrosion in mildly corrosive environments gives the steel good atmospheric corrosion resistance in polluted marine atmospheres.