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March 1, 2020

What are the Different Methods of Galvanization?

What are the different galvanizing methods?

  1. Batch Hot Dip Galvanizing
  2. Metallizing
  3. Electro Galvanizing
  4. Pre-galvanizing
  5. Sherardizing

When it comes to utilizing materials such as iron or steel for industrial, commercial, or construction purposes, it’s important that they’re able to resist any drastic changes in weather, or temperature. Steel, for example, already has highly-desirable qualities which make it one of the most preferred materials to provide durability to structures. However, the material is not entirely resistant to corrosion. As such, manufacturers apply different galvanizing methods in order to increase the level of resistance.

Galvanizing, or galvanization simply refers to a method of protecting different kinds of metals from corrosion, such as rust. Though there are other methods of achieving the same result, galvanizing is the most common. 

This method typically involves the application of a thin layer of zinc coating on a thicker metal in order to safeguard the metal from the surrounding environment. Without this method, the stainless steel, for example, would experience a higher rate of corrosion and would have to be replaced as the material itself crumbles, and its physical properties get weakened.

If you want to learn more about the different methods of galvanization, then it would be in your best interest to keep reading.

Batch Hot Dip Galvanizing

Before starting out any process of galvanization, the most important step is to ensure that the target metal has been subjected to rigorous cleaning. This is so, in order to avoid unnecessary dirt or debris from getting stuck under the surface of the zinc coating.

In batch hot dip galvanizing, which is also referred to as general galvanizing, the steel has been chemically cleaned to remove grease, oil, and oxides. Cleaning is the most crucial step in any galvanizing process, since the zinc coating won’t be able to react and subsequently adhere to the steel, making the zinc coating a part of it.

Batch hot dip galvanizing simply involves dipping the steel into a large bath of molten zinc – composed of more than 98% pure zinc and other additives like aluminum, for example, which gives the coating its shimmer, and other features to make the appearance more uniform.

Metallizing

 

Another form of galvanization is called metallizing. This process is often referred to as thermal spray. While metallizing is most commonly conflated with batch hot dip galvanizing, the two zinc coating processes differ in terms of how the zinc bonds with the base metal.

Metallizing is largely focused on the mechanical adherence of the zinc, on the surface of the steel for example. For this reason, it’s important that the steel is thoroughly cleaned and free from grease, oil, debris, or other oxides. The mechanical bond heavily relies on surface preparation, in much the same way that hot batch galvanizing does. The former, however, merely results in a zinc coating unlike the latter.

The resulting material can be used in a variety of ways – whether it be for functional or decorative purposes. 

Electro-Galvanizing

The first two galvanization methods involve the bonding of zinc through a metallurgical and mechanical process. Electro-galvanizing, on the other hand, results in a finish which has undergone an electrochemical process.

Starting out with surface preparation, the base metal, or steel, is once again dipped in a cold bath of molten zinc. As this is taking place, an electrical current is subsequently being run in the bath. In order to provide protection to the steel, the zinc serves the role of that of an anode – which is a positively charged electrode capable of attracting negatively-charged ions. 

Though it may seem confusing, the steel, in this process, is able to gain a greater resistance to corrosion through the cathodes – negatively-charged electrodes. The resulting finish appears to be blue-tinted through the application of conversion coatings which further adds to the corrosion resistance.

Pre-Galvanizing

 

Pre-galvanizing is also often referred to as mill galvanization. Though the name might seem to suggest it, pre-galvanizing does not necessarily denote the process before galvanization. 

To further illustrate, instead of the substrate of a steel material – like steel pipes, for example – a simple steel sheet is rolled through molten zinc. The sheet is then subject to further manufacturing processes, like being cut into shape before being recoiled once more.

Sherardizing

While the first two processes in this article are typically considered to be low-intensive processes of galvanizing, sherardizing is a bit different. While the goal of this process remains to be the same – adding a layer of zinc onto steel or iron in order to increase resistance against corrosion – this process is a more laborious one.

Sherardizing employs the use of a zinc powder, and not molten zinc bath this time around. The zinc powder has to be situated close to the surface of the metal in question, in order to create a relatively uniform diffusion-bonded coating.

Key Takeaway

The different galvanizing methods are all relatively the same in their aim – to add a layer of zinc coating which provides resistance against corrosion onto iron, or steel, for example. While some galvanizing methods are more labor-intensive, some are relatively straightforward, and would simply need the presence of a molten zinc bath.

While there exists a number of other methods of galvanizing, the guide above has hopefully adequately equipped you with some idea on what the process is all about.

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