What Is Galvanising?<\/h2>\n
Galvanisation or galvanising, as it is most commonly called, is a metal plating process in which an iron or steel component is coated with a thin layer of zinc. The zinc acts as a protective layer that shields the underlying surface from corrosion<\/a> and extends its lifespan. The process may sometimes be driven by electricity until a sufficient thickness of the zinc layer is developed. This layer is not discrete, i.e. the zinc merges into the steel at the surface and forms a strong metallurgical bond.<\/p>\n Galvanising is commonly used in places where the metal needs to endure harsh environments or in structural applications<\/a> where the metal needs to maintain its strength over many decades. The protective coating ensures that the base metal withstands challenging conditions without compromising its critical properties, such as tensile strength, elasticity and durability. The extensive utilisation of galvanised steel can be observed in the construction of bridges, guardrails and steel equipment in chemical plants.<\/p>\n The primary reason for galvanising steel is to increase its lifespan. Regular steel components, if not galvanised, can succumb to corrosion attacks and deteriorate quickly.<\/p>\n Even when embedded in concrete, steel products can corrode due to carbonation (exposure to carbon dioxide), moisture and high chloride levels. Applying a zinc coating improves the corrosion protection of the base metal and thereby enhances its durability.<\/p>\n Galvanising processes also provide the toughest coatings that can resist mechanical damage during transportation, storage and installation. The cost of installation is also low because galvanised components are ready to use upon arrival. Galvanised steel does not require any surface preparation, painting or inspection prior to installation.<\/p>\n Once installed, it provides a lifespan of over 50 years in rural areas and a minimum of 20 to 25 years in urban and coastal areas. The protective coating offers unparalleled protection by also covering sharp corners, recesses and other inaccessible areas. This feature is hard to find in some other coating processes.<\/p>\n Even when the coating is lost at a certain area, it still does not lead to corrosion because zinc has a higher negative reduction potential. This causes the zinc to oxidise instead of the iron, ensuring the safety of the application. To inspect the coating, only the physical condition of the layer is assessed. A close visual inspection<\/a> is sufficient. If the coating appears intact, we can be confident that no damage has occurred to the steel underneath.<\/p>\n Galvanised steel is generally a cost-effective<\/a> alternative compared to other methods, except for some large-scale applications. In the construction sector, galvanised steel may become so expensive that builders may abandon the idea of using it altogether when the budget is restrictive. A second disadvantage is that, although the zinc layer is resistant to red rust, it can still develop white rust<\/a> when continuously exposed to moisture.<\/p>\n There are several galvanising processes available, each with its own advantages and limitations. Let’s take a look at some of the most common galvanisation methods in use today.<\/p>\n Hot-dip galvanising is one of the most straightforward and economical galvanising methods. It is capable of coating a variety of complex shapes with relative ease. The surface of the material is cleaned of contaminants and any oxides before being dipped in a molten zinc bath. The bath of molten zinc applies a layer of zinc coating onto the steel component. The quality of the metallurgical bond is determined by how efficiently the surfaces were cleaned beforehand.<\/p>\n Electrolytic galvanising, also known as electrogalvanising, is the second most widespread galvanising method. It uses electrolysis to apply a layer of zinc onto a base metal, making it a form of electroplating<\/a>. In this process, the steel workpiece is placed in a zinc solution with a second electrode and then direct current is passed through it. The current ionises the zinc solution, depositing a pure zinc coating on the base metal. This process provides greater control over the rate of deposition and the layer thickness.<\/p>\n Sherardising is a type of galvanising process named after its inventor, Sherard Osborn Cowper-Coles. It uses thermal diffusion to create a zinc coating on ferrous metals<\/a>. In this process, the metal to be coated is placed in a container with zinc metal dust. The temperature of the workpiece is increased to 400-450 \u00b0C in the presence of this dust. The high temperature causes the dust to diffuse into the metal, forming a zinc-iron alloy.<\/p>\n Pre-galvanising can be understood as a type of hot-dip process adapted specifically for long steel sheets. In this process, the sheet is passed through a cleaning agent that prepares the material for galvanising. Once the metal sheet<\/a> has been cleaned, it is quickly passed through a molten zinc bath. The rapid movement enables the formation of a thin protective zinc coating that is more uniform than the one achieved in the conventional hot-dip galvanising method. This method provides the fastest turnaround times for sheet metal.<\/p>\n Why Galvanise Steel?<\/h3>\n
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<\/p>\nGalvanising Methods<\/h2>\n
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<\/p>\nHot-dip galvanising<\/h3>\n
Electrolytic galvanising<\/h3>\n
Sherardising<\/h3>\n
Pre-galvanising<\/h3>\n
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