Iron articles of the Roman and Saxon periods excavated at Hungate, York, were found excellently preserved in waterlogged anaerobic peaty soil at depths ranging 5 to 18 feet. Identified among corrosion products on one object were FePO₄ 2H₂O and Fe₃(PO₄)₂8H₂O (vivianite) in nearly equal proportions. Presence of many animal bones may account for some of the phosphate. Also identified on the iron surfaces were traces ot tannate, which may have come, not only from the soil but also from leather articles and cuttings found with the iron. In the soil sulphate reducing bacteria were found present but were not active. The characteristics of 18 soil samples from the site are tabulated. It was found experimentally that <i>D. desulphuricans is inactivated by tannic acid in concentrations as low as 0.01%. As a result of this work a method for the protection of present-day iron structures and -- AATA