Docks Pies and Jetties

The current marine facilities (ports, piers, breakwaters, etc.) are mostly composed of steel pipe piles or steel sheet piles, which are subjected to corrosion by water medium and humid gas due to long-term exposure to seawater, causing structural collapse and serious affecting the safe use of ports and piers. Therefore, it is extremely important to protect these steel structures from corrosion.

The coating serves as a protective layer against corrosion, but about 50% of the coating on the part located in the submerged area at the time of installation is lost, and 1-2% of the coating is lost annually in the splash zone and underwater area, resulting in a corrosion depth of steel ranging from 50 microns to 300 microns in these areas. The composition of water, oxygen concentration, marine organisms, and water speed also accelerate the thinning of steel materials due to corrosion.

Cathodic protection is a technology for corrosion protection that utilizes electrochemical methods. It involves using electrical technology to make all points on the metal surface have the same electrical potential, thus slowing down corrosion. Cathodic protection can extend the operating life of facilities, reduce maintenance costs, and ensure the continuous operation of docks and breakwaters. There are two ways to achieve cathodic protection: sacrificial anode cathodic protection and external current cathodic protection.

Sacrificial Anode Cathodic Protection Method involves connecting two metals with different activity levels and placing them in the same electrolyte. The metal with higher activity loses electrons and is corroded, while the metal with lower activity gains electrons and is protected. Since the more active metal is being corroded in this process, it is called sacrificial anode cathodic protection. Aluminum alloy sacrificial anodes and zinc alloy sacrificial anodes are commonly used in seawater. Cathodic protection method is also known as impressed current cathodic protection. It involves placing the anode in the marine environment and allowing the current to flow from the electrolyte to the protected structure and back to the power supply equipment. Since the current is forced to flow towards the protected structure, it is also known as forced current cathodic protection.

Suzhou BoGao can provide cathodic protection solutions for new or operating ports, jetties, breakwaters, etc. including sacrificial anode cathodic protection, external current systems, or a combination of both. BoGao is committed to meeting the requirements of various environmental conditions with international and domestic design standards. Before designing, we will conduct detailed engineering calculations based on national or international standards, which can make the cathodic protection system for submerged and underwater areas more effective.

The following table shows the corrosion rates in different regions. Cathodic protection can reduce the corrosion rate in the underwater and subsoil areas by nearly 95%. Special preventive measures are needed in the splash zone and atmospheric zone. It is recommended to use a cathodic protection system combined with coatings and PE sheathing to provide comprehensive protection for the pile columns.

Average corrosion values for steel sheet piles and steel piles:

Here are the data needed for the design:

• Types of Piles

• Length of Piles

• Designed Life of the System

• Length of piles on the seabed and above it

• Specifications for Pile Coatings

• Continuous welding method

• Floor plan

• Dangerous Area Segregation

• Facilities that are isolated from other structures

• Power Type and Availability

• Current cathodic protection systems