Do I Need An Anode On My Boat?

Most of the hulls of modern marine vessels are made of welded steel, and the special environment of ship operation makes the corrosion damage of ship hull and mechanical equipment quite serious. According to the statistics of the causes of ship accidents for many years, the average accident caused by hull structure damage accounts for about 8% of the total number of accidents, and a considerable part of them is caused by the reduction of hull strength due to ship corrosion. A failure analysis made by BRITOIL, a British marine engineering operating company, shows that 33% of all facility failures are caused by corrosion.

At present, the main methods of ship corrosion protection are organic coatings, sacrificial anodes, titanium anodes and applied current protection, or a combination of them, and other traditional methods. For safety reasons, titanium anode cathodic protection is generally used on ships, and applied current cathodic protection is generally not used. Installing more anode blocks will increase the ship's sailing resistance and cause over-protection, while less protection is insufficient and the ship still suffers from corrosion. Therefore, an appropriate amount of anodes must be installed, which requires a reasonable design.

According to the principle of cathodic protection, when implementing cathodic protection for metals, in order to achieve the best protection effect, it is necessary to pay attention to the arrangement and installation of cathodic protection. The following information on the arrangement and installation of titanium anodes is to be noted for reference.

1. Arrangement of sacrificial anodes

The arrangement of sacrificial anodes should follow the following principles:

(1) The sacrificial anodes required for the outer hull plates should be evenly and symmetrically arranged on the flow lines before and after the bilge keel and bilge keel to reduce the additional resistance of the hull;

(2) The sacrificial anodes required for the propeller and rudder should be evenly arranged on the stern hull plate and rudder, and no titanium anodes should be arranged on the hull plate within 300mm from the propeller blade tip and in the anode-free area of single-propeller ships;

(3) The titanium anodes required for submarine valve box and sonar transducer trap shall be arranged inside the box and trap.

2. Installation of titanium anodes

Titanium anode can be installed by welding or bolting. Generally speaking, the welding method is simple, with high fastness and low contact resistance, while the bolt installation is easy to replace without damaging the coating around and on the reverse side of the steel plate.

The installation of titanium anode should pay attention to the following points.

(1) Before installation, the back of the anode should be coated with insulating paint, and the surface of the hull at the installation should be coated with insulating paint or padded with other insulating materials to prevent the anode from falling off due to corrosion on the back of the anode, which also makes the back side ineffective, and the area used for the anode should be consistent with the design value;

(2) The surface of the anode shall not be painted or stained, and shall be protected before painting and launching;

(3)The anode should be welded at the designated position during installation, the back of the anode should be pressed tightly on the surface of the hull, and the iron foot burner should be repainted.