Corrosion Performance of Copper-Clad Steel Grounding Materials in Coastal Areas

Lightning protection and grounding systems in coastal areas face an additional challenge compared with inland projects: corrosion.

Salt carried by sea winds, high chloride concentrations in groundwater, and saline soils can work together to accelerate the corrosion of metal grounding materials. Under these conditions, the corrosion resistance of copper-clad steel grounding materials has become an important concern for many engineering projects.

Copper-Clad Steel vs. Copper-Plated Steel

First, it is important to distinguish between copper-clad steel and copper-plated steel, as these terms are sometimes confused during procurement.

Copper-clad steel is generally manufactured through processes such as continuous casting or other metallurgical cladding processes, creating a strong metallurgical bond between the copper layer and the steel core.

Copper-plated steel, on the other hand, generally refers to an electroplating process in which a relatively thin copper layer is deposited onto the steel surface.

In highly corrosive coastal environments, copper layer thickness and bonding strength are critical to service life.

If the copper layer is too thin, prolonged exposure to salt spray and corrosive soil may eventually damage the protective layer and expose the steel core. Once the steel core is exposed, corrosion can accelerate significantly.

Why Does Copper-Clad Steel Perform Well in Coastal Environments?

The key advantage of copper-clad steel is the inherent corrosion resistance of copper.

Copper generally has a relatively low corrosion rate in many soil environments. In neutral or mildly alkaline soils, a relatively stable surface film can form on copper, helping slow further corrosion.

Chloride ions can still affect copper under certain conditions, so copper should not be considered completely immune to corrosion. However, compared with ordinary steel, copper generally provides substantially better resistance to many coastal corrosion conditions.

Therefore, maintaining the integrity of the copper layer is critical to the long-term performance of copper-clad steel grounding electrodes.

Preventing Mechanical Damage During Installation

Damage to the copper layer can occur during transportation and installation.

Copper-clad steel grounding rods may be scratched or damaged when they are driven into the ground, particularly when they encounter rocks or other hard obstacles.

To minimize the risk of damage:

• Use a suitable driving cap or protective tool during installation;

• Avoid directly striking the copper surface with a steel hammer;

• Control the driving force and installation procedure;

• If large rocks are encountered, consider pre-drilling rather than forcing the rod into the ground.

For difficult geological conditions, pre-drilling can help prevent mechanical damage while also improving installation efficiency.

Protecting Connection Points

Connection points are another potential weak point.

When copper-clad steel grounding rods are extended using couplers, the copper layer around the connection area may be damaged during installation or connection.

If exposed steel is left unprotected, the connection can become a localized corrosion point.

After completing the connection, exposed areas should therefore be properly protected using suitable anti-corrosion tape, protective coatings, or other approved corrosion-control methods, ensuring that any exposed steel core is fully covered.

Burial Depth in Coastal Areas

Material selection alone is not enough. The grounding system should also be designed according to the local soil and environmental conditions.

Salt and chloride concentrations are often more significant near the surface in some coastal environments. Increasing the burial depth where appropriate can help reduce exposure to certain surface environmental influences.

However, burial depth should not be determined solely by coastal conditions. It should be based on soil resistivity, groundwater conditions, corrosion characteristics, frost depth, lightning protection requirements, and applicable engineering standards.

Don't Ignore Stray Current Corrosion

Another issue that deserves attention is stray-current corrosion.

Coastal areas may contain metro systems, electrified railways, DC traction systems, or cathodic protection installations. These systems can introduce stray currents into the surrounding soil.

When stray current leaves a grounding conductor and enters the soil, electrochemical corrosion can occur at the current discharge point.

Although copper-clad steel generally has good resistance to chemical corrosion, it should not be assumed to be immune to electrolytic corrosion caused by stray currents.

Where a potential stray-current source exists, the grounding system should be evaluated accordingly, and appropriate measures such as stray-current drainage or suitable electrical isolation should be considered.

How Long Can Copper-Clad Steel Last in Coastal Areas?

The actual service life of copper-clad steel grounding materials depends on several factors, including:

• Copper layer thickness;

• Bonding quality between copper and steel;

• Soil corrosivity;

• Chloride concentration;

• Installation quality;

• Mechanical damage;

• Connection protection;

• Stray-current conditions.

With compliant materials, proper installation, and adequate corrosion protection, copper-clad steel can provide long-term service in coastal grounding applications.

However, service life should never be determined by material type alone. A thin copper layer, poor bonding, installation damage, or inadequate connection protection can significantly shorten the actual service life.

Inspection and Maintenance of Existing Coastal Grounding Systems

For existing coastal grounding systems, monitoring changes in grounding resistance is particularly important.

If the grounding resistance shows a consistent upward trend over the years, possible causes include:

• Corrosion or reduction of the grounding conductor cross-section;

• Damaged or broken grounding electrodes;

• Corroded connection points;

• Changes in soil conditions.

Where the project is critical or conditions permit, periodic excavation inspections can provide a more direct assessment of the actual condition of the grounding materials and connections.

In coastal environments, long-term grounding reliability depends on both material selection and construction quality.

Choosing a suitable copper-clad steel grounding material is only the first step. Protecting the copper layer during installation, properly treating connection points, considering stray-current risks, and carrying out regular inspections are all essential to building a durable and reliable grounding system.