High quality Martyr Anodes are die cast and manufactured to strict quality standards through an ISO 9001 quality management system; Martyr Anodes offer maximum protection by keeping quality alloys free of impurities such as iron, which can compromise alloy performance; Three available – Use zinc (martyr I) for salt water, aluminum (martyr II) for brackish water, or magnesium (martyr III) in fresh water. Use; alternative anode alloys when changing water conditions; Offers low-cost cathodic protection of ocean-going vessels, structures and equipment constructed of iron, steel, aluminum, magnesium, and other metals