EDITORIAL Thermal zinc
Advantages of thermal zinc diffusion
“ Thermal zinc diffusion offers several advantages over other corrosion protection methods,” confirms Norton. The deep, diffused zinc layer offers excellent protection against rust and corrosion, even in harsh environments. This is because the zinc becomes an integral part of the steel, providing long-lasting protection.
The process also ensures a consistent and uniform coating, even on complex-shaped components with intricate details. The tumbling motion in barrels or the rotation of static containers allows for good contact between the zinc vapour and all surfaces of the parts.
As the zinc diffuses into the steel, there is minimal change in component dimensions, unlike electroplating, which can add a layer of material. It makes thermal zinc diffusion ideal for applications where precise tolerances are crucial.
Thermal zinc diffusion eliminates the need for hazardous chemicals like those used in electroplating. The zinc powder is typically the only material consumed in the process, making it a much eco-friendlier option.
The container is sealed and heated to a temperature range typically between 300 ° C to 430 ° C. The specific temperature selected depends on factors like the desired coating thickness and the type of zinc powder used. As the temperature increases, the zinc powder vapourises. These zinc vapours then come into contact with the hot steel surface.
The zinc atoms readily dissolve into the crystal structure of the steel to form a zinc-iron alloy layer on the surface. The depth of this layer depends on the process parameters like temperature and duration. The longer the parts are exposed to the high temperature, the deeper the diffusion, resulting in a thicker and more corrosion-resistant coating.
Once the required diffusion time is over, the container is cooled down. The cooling rate can also influence the final properties of the coating. The parts are removed, including any excess zinc powder. Depending on the application, a post-treatment like a passivation conversion coating or a paint layer might be applied for additional protection or aesthetics.
www. sabuildingreview. co. za
The diffused zinc-iron layer is an integral part of the steel substrate, reducing the risk of flaking or peeling, even under harsh conditions. Thermal zinc diffusion coatings can last for decades, depending on the application and environmental conditions. The deep diffusion and excellent adhesion contribute to the longlasting performance of these coatings.
“ Thermal zinc diffusion is a highly effective method to protect steel components in a variety of industries,” highlights Norton.“ Its ability to provide a deep, durable and environment friendly coating makes it an invaluable technology for ensuring the longevity and performance of critical steel parts,” he concludes. ■
About the International Zinc Association( IZA)
The IZA is the only global industry association dedicated exclusively to the interests of zinc and its users. Operating internationally and locally in Africa through the IZA Africa Desk, the IZA helps sustain the long-term global demand for zinc and its markets by promoting such key end uses as corrosion protection for steel and zinc as essential in human health and crop nutrition. IZA’ s main programmes are Zinc Use Research, Sustainability & Environment, Technology & Market Development and technical Communications.
In South Africa, the IZA plays a vital role in establishing the basis for the successful growth of the zinc industry by increasing awareness of zinc and its applications and benefits in key sectors and markets.
77