There are several brands such BlueScope Steel’s Zincanneal® that are essentially a form of Galvanized steel. But what is the process behind Galvanized steel? And, what is the coating actually made of? And, perhaps most importantly, what benefit do different types of coats have?
In this article we will cover a variety of different methods for applying zinc coatings and discuss how the thickness of the coating affects it’s durability and anti-corrosive properties.
What Are Some Common Types Of Zinc Coating Processes?
There are a variety of ways to apply a zinc coating as part of the Galvanizing process. Below are a list of the most common types of zinc coating processes:
– Zinc Electroplating
– Mechanical Plating
– Zinc Metal Spraying
– Continuously Galvanized Sheet
– Continuously Galvanized Wire
– Hot Dip Galvanizing
– Galvanized Pipe And Tube
In the sections below we will cover each of these processes in more detail, and explain how the application process affects the properties of the Galvanized steel.
The process of Zinc Electroplating involves placing the steel in a pool of zinc ions and then using an electric current to allow the zinc to coat the surface of the steel. The result is a very uniform coating due to the electro-chemical process.
Zinc electroplated coats are typically very bright with a thin layer. Due to the thinness of the layer, they are less durable than other forms zinc coating, however the coating is more uniform.
Mechanical plating involves using a reducing agent and zinc powder with glass beads to assist in bonding zinc to the surface of the steel.
Mechanical plating results in a thicker outer layer of zinc than electroplating. Typical coats using the mechanical plating process can be anywhere between 15 and 20 microns thick.
Sherardizing involves heating the steel itself to temperatures exceeding 400 degrees Celsius and then apply a zinc powder. The powder will bond with the steel due to temperature diffusion. The thick layer on the outside can measure up to 300 microns. Sherardizing is an outdated process, however, as it is time consuming and expensive.
Continuous Strip Galvanizing
The continuous strip galvanizing process is when coil steel is passed through a molten zinc solution in a monitored atmospheric environment. The results of this highly controlled process is a very accurate coating that an be measured between 7 and 42 microns thick.
Continuously Galvanized Wire
In the same way that continuous strip is Galvanized, the cleaned and processed wire is passed through a zinc metal solution in a controlled environment. The result is a tightly controlled process that results in a coating between 3 and 43 microns thick.
Galvanized Pipe And Tube
There two primary ways to galvanise complex objects such as pipe and tubing. The first process involves passing the objects through a zinc metal solution. The second process, is where only the outer area of the tubing passes through the zinc metal solution. Both of these types of galvanisation result in a thin layer of zinc. The result is steel with excellent formability and protective qualities.
Hot Dip Galvanizing
A bath of molten zinc is prepared and the steel is treated through a process such as picking. This type of zinc coating process results in a very thick layer of zinc alloy. The result is that hot dipped Galvanized steel is very well protected. This is a very popular method of immersion in regards to zinc coating.
Zinc Metal Spraying
The steel surface must be cleaned to a particular class level and then sprayed with zinc powder using an oxyacetylene or a plasma gun. This coating process results in a porous final product. This process is only applied when hot dip galvanisation is not an option – potentially due to the steel being an uncommon size or shape.
An Example of Galvanized Steel
Galvanized steel is used for a variety of applications. Different types of Galvanized have different properties depending on the process involved.
Zincanneal® is an example of an excellent Galvanized steel product that is still good for bending, roll-forming, welding and painting, whilst maintaining all the protective benefits of thicker zinc coatings. Zincanneal® can be found in everything: electrical cabinets, automotive panels, acoustic tiles, door frames and even on switchboards.
There are a variety of different ways to coat steel. Each ways provides it’s own benefits and drawbacks. Depending on the properties of the steel you are looking for, consider each of the above as options.