Corrosion Protection for Marine Structures — Effective Solutions and Advanced Systems

The Problem of Corrosion in Marine Environment

Corrosion is one of the primary threats to the structural integrity and safety of marine objects, including ships, port structures, offshore platforms, and various maritime facilities. Effective corrosion protection is crucial and must be approached as a comprehensive, systematic task.

Seawater is a powerful electrolyte, making it the most aggressive natural environment for metal structures.

Seawater is highly aerated, electrically conductive, and rich in salts, such as calcium, potassium, magnesium, sodium sulfates, and chlorides. When a marine structure interacts with seawater, an electrochemical potential forms, accelerating corrosion processes and significantly reducing the lifespan of infrastructure.

Types of Marine Structures Affected by Corrosion

Marine and port infrastructure is typically built using concrete, reinforced concrete, and steel frameworks. These include:

• Fixed, floating, and semi-submersible platforms 
• Piles and gravity-based structures 
• Ship hulls made from special shipbuilding steel alloys 

The intensity of corrosion varies across different sections of a structure. Marine corrosion is typically categorized into three distinct zones:

1. Atmospheric Zone (Above Water) — Exposed to seawater spray and high oxygen levels, leading to atmospheric corrosion.
2. Splash Zone and Tidal Zone (Variable Moisture) — The most aggressive zone, located between the highest and lowest sea levels due to wave action and ship displacement.
3. Submerged Zone (Below Water Level) — Corrosion occurs at a slower rate due to limited oxygen availability.

Factors Influencing Corrosion Rates

Salinity levels (chloride concentration)

• Oxygen content (O₂) in seawater 
• Temperature and water flow rate 
• Surface composition and post-treatment conditions 

In the splash and tidal zones (Zone 2), metal loss can reach 1.25 mm per year, whereas in the submerged zone (Zone 3), corrosion rates are lower, averaging 0.06–0.15 mm per year.

Corrosion Protection Methods for Marine Structures

1. Corrosion-Resistant Materials and Coatings

• Special corrosion-resistant alloys are highly effective but costly. 
• Protective coatings (epoxy, coal tar, urethane, vinyl resins) provide temporary corrosion resistance but are subject to abrasion and degradation over time. 

2. Cathodic Protection (CP) Systems

Cathodic protection is a highly effective and cost-efficient method for protecting marine structures from corrosion. It is implemented in two ways:
Impressed Current Cathodic Protection (ICCP)

• A DC power source is connected to the protected surface (cathode), while sacrificial anodes or metal electrodes with special coatings (platinum-group metals) serve as the anode. 
• This system forms a protective layer of insoluble salts, preventing corrosion. 

Sacrificial Anode Cathodic Protection (SACP)

• The structure is connected to sacrificial anodes made of zinc, aluminum, or magnesium alloys. 
• These anodes gradually dissolve, preventing corrosion of the primary structure. 

Advantages of CP Systems:

• Long-term protection
• Cost-effective and easy to maintain
• Effective in aggressive marine environments

Cathodic protection is an incredibly low-cost method of corrosion protection when considered over the long term.

Developing a Comprehensive Corrosion Protection Strategy

To fully protect ships, piers, offshore platforms, and marine infrastructure, a systematic approach is required:

• Apply corrosion-resistant coatings in Zones 1 and 2. 
• Implement ICCP systems in Zones 2 and 3. 
• Install sacrificial anodes in Zone 3, especially in areas where ICCP installation is impractical. 

This integrated protection strategy has been fully developed and implemented by PSS Corporation.

PSS Corporation: 30 Years Of Corrosion Protection Expertise

For over 30 years, PSS Corporation has been a leading provider of electrical and corrosion protection solutions for shipbuilding, oil & gas, and energy industries. The company collaborates with international markets and offers a wide range of cathodic protection systems for marine and coastal structures. Additionally, PSS Corporation is open to technology transfer and has the expertise to set up production facilities abroad in partnership with international manufacturers.
By implementing innovative corrosion protection technologies, PSS Corporation helps extend the service life of marine infrastructure, reduce maintenance costs, and ensure the long-term sustainability of offshore and coastal facilities.