Abstract: An aluminum marine anode is constructed in association with exposed activator surfaces. The surfaces are preferably provided by casting the aluminum anode with a partially exposed core of activator material in place and suitably configurated to provide good conductive contact between the aluminum and the activator. Materials which exhibit a surface potential less negative than about -300 millivolts with respect to a silver-silver chloride half cell function as activators, copper being preferred. Aluminum alloyed with zinc and tin is the preferred anode material.

Abstract: An aluminum marine anode assembly is constructed by casting a mass of marine aluminum alloy as an anode with a partially exposed core of activator material in place. The anode is configurated to provide good conductive contact between the aluminum alloy and the activator. Copper and alloys of copper are the preferred core materials. Aluminum alloyed with zinc and tin is the preferred anode material. The anode assembly is attached to a ferrous hull by means of special low resistance surface mountings.

Abstract: An electrical system for measuring the relative level of protection afforded a structure against corrosion caused by electrochemical reaction where such structure is so protected by a system of sacrifical anodes. This instrument is constructed with a magnesium alloy anode and calibrated to read with reference to any of the three standard voltage reference half cells currently used in the industry, specifically copper-copper sulfate, silver-silver chloride, and saturated calomel.

Abstract: A cathodic protection system for metallic structures disposed in contact with marine brine includes a plurality of sacrificial marine anodes mechanically linked in a chain suspended above the brine with a portion of the chain immersed in the brine. The chain of anodes is electrically coupled to the structure, and means are provided for selectively releasing and retrieving the chain from storage to correspondingly increase or decrease the length of chain immersed in the brine.