Cathodic protection of wharf steel piles

Cathodic protection of wharf steel piles

The combined corrosion protection method of coating and cathodic protection is adopted for the corrosion protection of the port wharf, and cathodic protection can also be adopted for the underwater area, while the coating method is adopted for the area above the average low tide line. Cathodic protection can adopt sacrificial anode cathodic protection, or forced current cathodic protection, or a combination of the two, mainly depending on the structure, clothing environment, power supply, equipment reliability, operation management and other factors of the comprehensive effect of economic and protection effect.

Generally speaking, the protection current density of Luolou structure decreases with the extension of time after the use of cathodic protection, mainly because of the formation of cathodic protection deposition film on the surface of the structure, which can hinder the diffusion of oxygen. After the structure with coated layer adopts cathodic protection, the protection current density increases with the extension of time, mainly because the coating layer gradually aging, the damage rate increases, and the cathode deposition film formed is not enough to reach the current density as small as that under the protection of intact coating layer. The coating structure can improve the distribution of cathodic protection current density and protection potential, especially for the forced current cathodic protection system.

Forced-current cathodic protection should be given priority to estuary port facilities where water quality varies greatly. In order to prevent overprotection, the sacrificial anodes can be kept far away from the protected surface, or a variable resistor can be connected between the sacrificial anodes and the protected body to control the output current.

For sea port wharf facilities corrosion, above the tidal range zone parts should ShiJiaHou slurry coating corrosion prevention, for the underwater part, most of the past with impressed current cathodic protection, with the improvement of the performance of the aluminum alloy anode and cathodic protection of accumulating experience parameters, using sacrificial anode cathodic protection rapidly increase the number of ports, The selection of the way to implement protection is mainly considered from the following aspects: 1, the reliability of the protection system 2, the influence of adjacent structures 3, the protection current requirement 4, the complexity of the structure 5, the structure life 6, environmental conditions and so on

Sacrificial anode layout and installation:

The sacrificial anode should be evenly arranged on the protected structure facilities and should be 300mm lower than the lowest tide level. The sacrificial anode of the water drum cable should be arranged symmetrically at the bottom of the water drum.

There are two requirements for the installation of the sacrificial anode: 1. Ensure sufficient strength; 2. Ensure that the contact resistance between the sacrificial anode and the protected body is less than or equal to 0.005 ω.

The sacrificial anode can be installed by welding method or bolt fixing method. The commonly used installation methods are: 1, hanging plate fixing method 2, hook fixing method 3, Angle steel fixing method 4, bolt fixing method

Impressed current cathodic protection:

1. Calculate the protected area of the protected body, in addition to the average low tide immersed sea water and sea mud area, the area of the tidal range area and the area of the accessory structure should be calculated together.

2. Calculation of protection current: according to the protection area and initial protection current density or maximum protection current density, the protection current required by the cathodic protection system is calculated, and 1.25-1.5 times of it is taken as the total current requirement.

3, the selection and number of auxiliary anodes: used for port port forced current cathodic protection of the auxiliary anodes are: high silicon cast iron, metal oxide, etc., the general requirements of the anode and the protected body at least 1.5m distance, the greater the distance between the anode and the protected body, the more uniform the protection potential.