All steel sheet and tube products consist of two basic elements: carbon and iron. However, they may vary in composition and manufacturing processes. Hot-dipped galvanized steel coils and cold-rolled steel coils are two such products, each with distinct properties and applications.
Galvanized steel, commonly known as hot-dipped galvanized steel, is produced by immersing steel products in molten zinc. This process creates a protective zinc layer that is rapidly oxidized in the open air. Zinc is less reactive than iron in the redox process, making it an effective protective coating. This zinc layer significantly enhances the steel’s resistance to corrosion, extending its lifespan and durability in various applications.
Cold rolling is a steel forming process that occurs at temperatures below the steel’s recrystallization point. This method, using various types of rolls, results in products with higher dimensional accuracy compared to hot rolling. Cold rolled steel is well-suited for applications that require precise dimensions and smooth surfaces. The primary products of cold rolling are sheets and coils, but the steel can also be further shaped into cylinders, I-beams, and tubes to meet specific requirements.
Cold rolled steel and galvanised steel are produced through different processes serving distinct purposes. Cold rolling is a method used to shape steel into precise dimensions and smooth surfaces, while galvanising involves coating the steel with a layer of zinc for corrosion protection.
Cold rolled steel products can indeed be galvanised. However, galvanised steel has limitations: it is not suitable for high-temperature environments, and the protective zinc layer can be compromised if the surface is scratched.
Galvanised steel products can be produced from both cold-rolled and hot-rolled steel. Generally, hot-rolled steel has a better yield strength than cold-rolled steel because the cold-rolling process breaks down the grain structure of the steel, while hot-rolling improves it. Cold-rolled steel has better surface conditions than hot-rolled steel. The customer should choose the right steel for your different applications.
Yes, fire protection can be effectively applied to hot-dipped galvanised steel using two main methods: cement-bonded concrete and fire protection coatings. Cement-bonded concrete comes in two types: dense and lightweight. Dense cement-bonded concrete is commonly used for outdoor structural elements that are exposed to potential impacts.
Lightweight cement-bonded concrete is typically used where weight is a concern or in areas with lower impact risk. However, it is more susceptible to moisture penetration compared to dense concrete. Therefore, it is crucial that the lightweight material fully covers the area and adheres to the thickness specifications provided by the steel coil manufacturer.
Fire retardant coatings, on the other hand, are reactive materials that foam when a certain temperature threshold is exceeded. This foam acts as an insulating layer, reducing heat transfer to the steel, while the ceramic binder provides additional protection against excessive heat.
Regardless of the fire protection method used, challenges remain with fireproofing hot-dipped galvanised steel. The porous nature of fireproofing materials can lead to deterioration, allowing water and other corrosive elements to reach the underlying steel.
Fireproofing serves as an insulating layer, protecting the underlying galvanised steel from corrosive elements and moisture. However, if the fireproofing material deteriorates, it can trap moisture and corrosive agents, which may accelerate the corrosion of the galvanised coating. Additionally, fireproofing can be challenging to remove and complicates the detection of moisture and other corrosive elements underneath the material.
