With infrastructure demands rising across Africa, selecting the right materials for structural and roofing applications has become a critical decision for engineers, architects, and developers. The International Zinc Association (IZA) Africa Desk highlights the enduring performance and versatility of hot dip galvanized structural steel and continuously galvanized roof sheeting, particularly in the face of tough environmental conditions.

“Whether you are designing for deep South African underground mines or the corrosive local coastline, galvanizing provides a proven and cost-effective corrosion protection system that extends the life of steel by decades,” says Simon Norton, Director of IZA Africa.

Hot dip galvanized steel, coated with a layer of zinc plus an organic coating, is especially valued in structural and roofing applications for its durability, low maintenance requirements, and lifecycle cost benefits. When exposed to the atmosphere, zinc forms a protective patina of complex zinc carbonate that shields steel from corrosion, even in aggressive environments. Zinc offers cathodic protection to the underlying steel as well. “It is a double whammy of benefits!” comments Norton.

Norton advises that while standard hot dip galvanized steel performs well in inland areas with low to moderate corrosion exposure, additional considerations are necessary for coastal or industrial zones. Inland in South Africa, the extensive deep underground mining industry will benefit substantially from the use of galvanized steel for mine shaft steel and buntons, as these are exposed to very corrosive mine waters and conditions underground.

“In sea salt sprayed coastal areas, it is essential to use thicker zinc coatings on steel sheet or duplex systems, namely galvanizing followed by paint, to withstand the increased corrosive impact,” explains Norton. A site-specific corrosion risk assessment (using ISO 9223) should guide the choice of coating type and thickness for continuous galvanized roof sheeting, with SANS 121 (ISO 1461) as a benchmark for hot dip galvanizing standards in South Africa.

For roof sheeting, continuous galvanized (zinc coated) steel is widely used due to its formability and corrosion protection. However, it cannot be used without a primer and organic overcoat, what is known as a duplex system. Hence products such as Chromadek are specified. Zinc-aluminium coated products such as Bluescope Colourbond and Safal Colourplus can also be specified, particularly in coastal zones (the ultra-version).

This is due to enhanced corrosion resistance in marine atmospheres resulting from the zinc-aluminium coating layer on the steel. However, again bear in mind that all these roof and cladding products have an organic coating on top of the zinc or aluzinc layer to provide that extra duplex system and protection from the external environment, notes Norton.

Galvanized steel contributes to sustainability goals, aligning with global green building practices. Zinc is a natural, recyclable metal, and galvanized steel can be reused or recycled without loss of physical properties of the basic contents namely steel and zinc.

“Galvanizing supports Africa’s infrastructure development not only by increasing material lifespan, saving valuable capital and by lowering total environmental impact,” says Norton. “IZA Africa is committed to providing expert knowledge about appropriate zinc applications to ensure safe, economical, and long-lasting infrastructure across the continent.”