A description is given of the source of metal corrosion products that cause wood deterioration around corroding metal in wet wood, such as in rail ties, wooden vessels, and exposed wood construction. Corrosion of isolated steel fasteners in wood and the formation of acid condtions around the corroding steel is explained in terms of crevice corrosion. The source of acid and alkaline conditions around corroding metals undergoing galvanic corrosion and the source of alkaline conditions around cathodically protected metal are also explained. Several prevention methods are included.