When metal structures such as ships, offshore platforms and docks are placed in seawater, the use of DC electrical equipment on these structures will cause stray current interference, such as forced current cathodic protection.

As a hull, stray current mainly occurs during ship repair, berthing and maintenance, because it is often necessary to use electric welding or other electric welding current through the hull during this period. Because of stray current corrosion of many cases, the fast 3 months will be corrosion perforation, what is more, a dalian shipping brigade of a ship, parked on the shore, using a single line for shafting welding work, lasting about 5h, corrosion damage to a cast steel propeller.

After the distribution and direction of the stray current are determined through detection, the sacrificial anode can be installed on the direction side to guide the stray current artificially, that is, the stray current does not flow into the sea water through the hull, but transfers the corrosion to the sacrificial anode through the sacrificial anode.

In seawater and fresh water medium, zinc - aluminum - cadmium or aluminum - zinc - indium sacrifice anode can be used, the anode composition should comply with GB/T 4950 and GB/T 4948 regulations; In fresh water medium, magnesium alloy sacrificial anode can be selected, and the anode composition should conform to GB/T 17731-2007.