Since different manufacturing processes were used in producing the iron of the past, it is reasonable to ask whether such differences may have an effect on corrosion resistance. The findings of corrosion science regarding the corrosion resistance of iron and steel are summarized briefly. While composition affects corrosion resistance in outdoor air, most corrosion in neutral water is unaffected by the chemical composition of the steel, but instead depends almost entirely upon conditions in the environment. Several specific instances of apparent corrosion resistance in older steel are examined, and in all cases some environmental condition can be found which favors corrosion resistance.