Solutions to Protect Ships from Corrosion

Corrosion Damage and Its Consequences

Corrosion-mechanical degradation leads to the failure of a large number of hull structures in ships and floating technical facilities. In addition to the environmental dangers posed by such accidents (environmental pollution, loss of energy resources), they also cause significant economic losses: equipment damage, repair costs, and operational downtime. Around 10% of metal is irreversibly lost, dissipating as oxidation products.

The production of equipment for monitoring and preventing corrosion on underwater parts of ship hulls is a key competence of PSS Corporation.
Depending on the type of corrosion and the conditions under which it develops, various protection methods are applied to ship hull structures. The choice of a particular method is determined by its effectiveness in a given case and its economic feasibility. Any corrosion protection method alters the progression of the corrosion process—either by slowing it down or stopping it completely. One of the most reliable ways to protect steel in seawater from corrosion is cathodic protection.

PSS Corporation provides two solutions of cathodic protection: sacrificial anode (galvanic, or SACP) cathodic protection and impressed current cathodic protection (ICCP).

Impressed Current Cathodic Protection on Ships

This is the most reliable and economically advantageous method for protecting the underwater parts of marine infrastructure. The benefits of cathodic protection for offshore platforms include:

• Complete suppression of corrosion on hull plating and welds
• Reduction in the required corrosion allowance on hull thickness
• No need for replacement during the ship’s entire service life
• Remote monitoring and control

Practical experience and calculations show that for vessels with a displacement of over 3,400 tons, impressed current cathodic protection is optimal due to the significant weight reduction compared to sacrificial anodes. For vessels over 6,000 tons, impressed current cathodic protection also reduces the total cost of protection.

The main components of this system include:

• Transformer rectifier units (power supply) –> They protect by shifting the potential on the ship’s hull, where only the cathodic process occurs, thus slowing corrosion. The units are available in various configurations and can be customized upon the request.
• Hull anodes – The anodes are connected to the CP power supply and discharge protective current into the water. Different types of anodes have been developed for different operational zones, including the Arctic. They are mounted in a way that does not interfere with vessel navigation.
• Silver/silver chloride reference electrodes – Available in polymer housings or protective cofferdams. They measure potential and are used in automatic monitoring and control systems for cathodic protection.
• Cable – Special cathodic protection cable is resistant to petroleum products and other aggressive environments.

Sacrificial Anode Cathodic Protection for Ships

Sacrificial anode protection is cost-effective, simple, and easy to implement. The anodes dissolve slowly, protecting the structure they are attached to. They are made from aluminum, zinc, or magnesium alloys, with an embedded steel core for mounting. Anodes are manufactured in various sizes based on customer requirements. Their shape is chosen according to the installation location and operational conditions. For ship hulls, streamlined anode shapes are considered optimal.