Verification of stray current corrosion

The corrosion damage rate of stray current is very fast, and it is not related to the steel quality of the ship. Generally only half a year to a few days. Some even destroy the shell or parts in a few hours. The shape of corrosion is usually pit or perforation. There is black powder mud rust in the corrosion pit, and white cathode deposit is attached to the corresponding cathode. Corrosion is concentrated in areas with low resistance and easy discharge, such as paint peeling and damaged parts, sharp corners and edges protruding, and the most serious corrosion is on the side of dock or power supply.

Because the order of magnitude of stray current is very large, the corrosion of stray current can not be prevented by conventional cathodic protection, and the dissolution of sacrificial anode will be greatly increased. The corrosion caused by AC stray current is only 1% of that of DC. When there is stray current, the potential value of the hull is obviously deviated from the normal potential value of the ship.

After the distribution and direction of stray current are determined, sacrificial anode can be installed in the flow direction side to guide the stray current away artificially. That is to say, 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. When the current discharging method of sacrificial anode is adopted, the sacrificial anode can provide cathodic protection to the hull after the welding operation is stopped.

When there is a power plant, DC electrified railway or river crossing cable near the port where the ship berths, attention should be paid to the existence of stray current, and the direction and position of stray current source should be judged by measurement.

It is not allowed to use sea water and river water for discharge and voltage reduction, and it is not allowed to use damaged cables to avoid stray current. When long-term welding operation is carried out on a large ship, the whole set of welding machine should be moved to the hull. The ship power supply system and electrical equipment must be well insulated and checked regularly to avoid leakage.

Shandong Linyi Bosi conductive materials Co., Ltd. is a high-tech enterprise specializing in the production of MMO flexible anode, conductive polymer flexible anode and titanium coated anode, mainly providing cathodic protection technology, engineering design, installation and technical services.