The mining industry, reliant on robust infrastructure to transport valuable resources, faces a significant challenge in protecting its wharves and submerged structures from the relentless forces of corrosion. Traditionally, Cathodic Protection (CP) systems have been the go-to solution. However, Duplex Coated Steel (DCS), a combination of hot dip galvanizing and a high performance organic coating, offers a more durable, cost-effective, and environmentally friendly alternative.

Hot dip galvanizing of a steel structure in molten zinc at around 450 oC

The Limitations of Cathodic Protection ( CP) Systems

While CP systems effectively mitigate corrosion by applying an electrical current to a metal structure, they come with several drawbacks. Firstly, they require frequent and constant monitoring and maintenance, including anode replacement and power supply checks. This ongoing upkeep can be costly and time-consuming, especially for remote or underwater structures and made worse when staff are unavailable to carry out checks.

Secondly, CP systems can be susceptible to damage from physical impacts, such as vessel collisions or marine debris. Any damage to the anode or cable system can compromise the system's effectiveness, leading to accelerated corrosion. Additionally, CP systems can interfere with other electronic equipment, such as underwater sensors and communication devices, potentially disrupting operations.

The Advantages of Duplex Coated Steel

Duplex Coated Steel offers a comprehensive approach to corrosion protection, combining the benefits of both galvanizing and organic coatings.

• Long-lasting Protection: The zinc coating provided by hot dip galvanizing acts as a sacrificial anode, protecting the steel substrate from corrosion. The organic topcoat provides the first barrier against the environment including moisture and oxygen and underneath it the tough hard galvanized zinc layer acts as a second barrier, further extending the lifespan of the structure.
• Reduced Maintenance Costs: Unlike CP systems, Duplex coatings require minimal maintenance. Intermittent inspections are sufficient to ensure the integrity of the coating. This significantly reduces operational costs and downtime. At a recent conference on concrete repair and rehabilitation in October 2024, a CP expert suggested that CP systems must be inspected at least 4 times per annum. At many sites this is completely impractical and in many countries would not happen.
• Environmental Friendliness: Duplex coating systems are environmentally friendly as they do not rely on electrical power or sacrificial anodes. This makes them a sustainable choice for mining operations.
• Increased Durability: The combination of galvanizing and organic coating provides excellent resistance to abrasion, impact, and ultraviolet radiation, ensuring the long-term durability of the structure.
• Ease of Installation: Duplex coated components can be easily fabricated and installed, reducing construction time and costs.
• Improved Safety: The robust protection offered by Duplex coated steel can enhance the safety of mining operations by reducing the risk of structural failures and accidents.

Real-world Applications

Duplex Coated Steel ( DCS ) has been successfully used in various mining applications, including:

• Offshore Platforms: DCS provides superior protection against harsh marine environments, including saltwater corrosion and wave impact.
• Piles and Jetties: DCS offers long-lasting protection for these critical infrastructure components, reducing the need for frequent repairs and replacements.
• Submerged Pipelines: The combination of galvanizing and organic coating ensures the integrity of pipelines, preventing leaks and minimizing environmental impact.

Duplex Coated Steel offers a compelling alternative to traditional CP systems for mining wharves, immersed process plant steel  and submerged structures. Its superior durability, low maintenance requirements, and environmental friendliness make it a cost-effective and sustainable solution.7 By embracing Duplex coatings, mining companies can enhance the longevity and safety of their infrastructure, while minimizing operational costs and environmental impact.

IZA