The building and construction industry forms the backbone of engineering growth in South Africa and across Africa. It supports crucial infrastructure like rail networks and underpins vital economic activity, including mining. However, beneath this robust foundation lies a persistent, silent enemy: corrosion.

Often unnoticed until damage worsens, corrosion severely impacts steel structures. This silent destroyer compromises safety, durability and long-term economic sustainability. Fortunately, zinc offers a powerful solution, emerging as a steadfast protector against this detrimental force.

The role of steel and the threat of corrosion

Steel has become a cornerstone of construction due to its strength, versatility and cost-effectiveness. From buildings to bridges, it forms the structural framework of countless infrastructure projects. However, steel’s significant vulnerability to corrosion presents challenges with long-term consequences for safety and economic viability.

When steel interacts with moisture, chlorides and oxygen, an electrochemical reaction occurs. This reaction converts the steel into rust, a process that, although gradual, can lead to severe outcomes. Corrosion weakens critical structural components like beams and columns, resulting in cracks, deformation, or, in the worst-case scenario, structural failure.

Weakened steel presents safety hazards and increases lifecycle costs due to frequent maintenance, rust removal and replacements. According to Simon Norton, Director of the International Zinc Association (IZA) Africa: ‘The true cost of corrosion is not only measured in capital expenditure but also in the disruptions it causes to economies and the environment.’

How zinc safeguards steel against corrosion

Zinc acts as a protective guardian, shielding steel from corrosion in several ways. To understand this protection, one must first explore why steel corrodes.

The corrosion process Steel, composed of iron, carbon and other trace elements, reacts with water and oxygen through electrochemical processes. This reaction leads to the formation of rust over time. Coastal, polluted, or humid environments severely speed up this process.

Zinc: The shielding element As a more reactive metal, zinc provides ‘sacrificial protection’ for steel. Coating methods like hot-dip galvanising or zinc thermal spraying allow zinc to corrode first, creating an oxide, hydroxide, or carbonate layer. This layer shields the steel from continued exposure to water and oxygen. Even when the coating is scratched or worn, zinc continues to protect the steel through cathodic action. As Norton explains: ’Zinc doesn’t just cover the steel; it actively protects it, even under harsh conditions.’

Applications of zinc in construction

Zinc is versatile, making it a vital material across the construction sector. Common methods include:

Hot-dip galvanising Steel is immersed in molten zinc, creating a tough, durable coating. This method is widely used for roof sheeting, structural steel and pipes, ensuring decades of protection.

Zinc-rich paints These paints contain high concentrations of zinc and are ideal for touch-ups, complex surfaces, or applications with irregular shapes.

Zinc thermal spraying This technique sprays molten zinc onto steel surfaces, forming thick protective layers. It is particularly suited for harsh, marine environments.

The choice of protection depends on several factors such as environment, cost-effectiveness and application.

Cost-effective and sustainable solutions

Hot-dip galvanising provides longevity and economic benefits for new steel structures. For existing infrastructure exposed to extreme weather, zinc-rich paints and thermal spraying offer effective alternatives.

In addition, zinc contributes significantly to sustainability by reducing waste and minimising the need for reconstruction, which aligns with the construction industry’s growing emphasis on environmental consciousness.

Zinc: Vital to South Africa’s infrastructure growth

Zinc ensures that steel supports South Africa’s essential infrastructure for decades. By protecting structural integrity, reducing lifecycle costs, and extending service life, zinc plays a vital role in meeting the industry’s demands for resilience and sustainability.

’Corrosion may be the silent destroyer of steel, but zinc stands as a proven and reliable guardian,’ concludes Norton.