Coated Steel Sheets
General information on coated steel sheets
Steel sheets and plates can be coated with various materials to induce or reinforce desirable characteristics. Such characteristics may encompass a protective function or particular design aesthetic. Coatings help make steel products more versatile and thus applicable in a wider range of applications and industries. Steel & metal products can amongst others be galvanised, passivated, chrome or phosphate coated. To suit your industry specific requirements, the Kloeckner online shop stocks a range of coated steel and metal products with different characteristics.
Different steel coatings
Galvanizing describes a process in which a zinc layer is applied to steel to prevent rust from forming. Steel can either be hot dipped galvanised or electrogalvanized. During hot dip galvanizing, steel is immersed in molten zinc which triggers the formation of a zinc-iron alloy. The hot dipping method creates thick zinc coating which is most effective against corrosion.
During electrogalvanizing an electric current is run through a zinc solution which oxidises zinc on the surface of the immersed steel product. This process is sometimes also referred to as electroplating. Electroplating zinc offers a few advantages over hot dipping including a lower thickness of deposits and a brighter more visually appealing aesthetic.
When a thin layer of chromium is electroplated over another metal surface this is referred to as a chrome layer. The chromium oxide inherent to chrome helps protect underlying steel from corroding. Chromium coatings hence act as a corrosion inhibitor but also as a primer, design aesthetic or help retain electrical conductivity. Generally, chromate conversion coatings are used to passivate steel.
The process of converting a steel surface to iron phosphate is referred to as phosphating. Phosphating is commonly used as a pretreatment, often in conjunction with other substances that hinder corrosion. The main types of phosphate coatings are manganese, iron and zinc. These are inherent to a phosphoric acid solution that is applied through immersion or spray painting. Phosphate coatings are not only popular corrosion inhibitors but also help reinforce lubricity or act as a foundation for subsequent surface treatments (ex. painting).
Industries that utilise coated steel and their benefits
Applying different coatings to steel products heightens their versatility and thereby broadens the range of application and industries. Some coatings are geared more towards improving corrosion resistance and strength for example as a finish to harden industrial tooling. Galvanised sheets with their thick gray, drippy finish greatly outlast zinc electroplating and are therefore more suitable for direct exposure to the elements. They can therefore be found in metal roofing as metal roofing sheets. Irregularities in coat thickness may however interfere with fasteners.
Other types of coatings are more refined and used in industries where a tasteful finish is deemed most important. Electroplated zink coatings for example are smooth and shiny, making them popular in many design applications. Chrome finishes are also often used for their design appeal as a decorative trim on cars & motorcycles. Chromate conversion coatings are applied to many everyday items including hardware and tools and easily recognized by their distinctively iridescent, green/yellow finish. Apart from being merely decorative, a chrome finish also provides resistance to rusting, the smooth finish eases cleaning procedures and reinforces surface hardness.