Hot dip galvanizing (HDG) is a widely used process or method for protection of metal surfaces made of steel or iron from corrosion. In this process, a four-layer zinc coating is formed on the metal surface electrochemically. The steel or iron base is passed through a molten bath of zinc at 460 degree centigrade of temperature which allows the zinc to bond with the steel or iron base at a molecular level.
Hot dip galvanizing process is considered to be far more superior to all other zinc coating systems. These include:
Metallizing: In this zinc coating method, zinc in wire or powder form is sprayed onto the steel base that needs to be protected from corrosion. As a result, it only offers a barrier instead of allowing zinc to bond with the metal base. So, what you get is limited protection from rusting or corrosion. This is however not the case with hot dip galvanizing process. In this, a four-layer corrosion resistant surface is created on the metal base. Even if the hard zinc-steel alloy barrier gets damaged, the electrons in the zinc coating will sacrifice themselves to prevent corrosion of the base metal. In addition, the topmost layer of zinc, when reacts with oxygen, moisture and carbon dioxide in the air, it creates an impermeable layer of zinc carbonate to provide further protection from corrosion.
Electroplate Galvanizing: Like HDG, in this process too, zinc is electrochemically applied to the steel base. However, the thickness of the coating formed on the surface is less when compared to that formed by the hot dip galvanizing process.
Mechanical Galvanizing: In this method, the zinc powder is mechanically welded to the steel or iron items using the energy generated by a large rotary drum. However, this method is ideal only for fasteners or other small items. On the other hand, HDG is used in several applications, including automotive body parts, handrails, consumer appliances, roofing and walling, heating and cooling duct systems in buildings, and metal pails.
Zinc Paint: Zinc paint is the most commonly used repair methods for protection from corrosion. However, here the performance depends on the quality of application. This in turn depends on a number of factors like condition of the steel surface, surface preparation, weather conditions, and the skill of the painter. Besides, it is just a coating unlike hot dip galvanizing process where the zinc bonds to steel metallurgically, providing three types of protection: effective barrier, cathodic protection, and the zinc patina (the hard zinc carbonate layer).
Continuous Galvanizing: This zinc coating system is ideal for very thin sheets of steel and has several properties that are similar to that of HDG. In this method, coils of steel are made to react with molten zinc to form a protective coating on the surface. However, the coating formed is very thin.
So, when it comes to effective protection from rusting and corrosion, no other process can beat HDG.