Evaluation of the corrosion resistance of various iron specimens with different date and process of making found that ancient iron was much more corrosion-resistant than modern industrially-made iron due mainly to the soundness of the passivation film on the surface. Analyses by atomic absorption and neutron activation showed that high quality ancient iron contained only several tens parts per million of manganese and silicon, whereas present day iron contains as much as thousands parts per million of manganese and silicon. Superior corrosion resistance and workability were observed on the specimens prepared by a traditional iron making process which had been kept in secret in the Kurabayashi family for several hundred years. The Kurabayashi iron is characterized by carbon in the form of vermicular graphite in spite of its low carbon content (carbon 0.4 percent by weight); it contains about 50 parts per million of manganese after forging. It is concluded that present day iron would approach the high quality of ancient iron if manganese and silicon contents were reduced below 200 parts per million.