Difference Between Galvanised Steel and Stainless Steel

Main Difference – Galvanised Steel vs Stainless Steel

Steel is a metal alloy. It is composed of iron and some other elements. Steel is widely used all around the world due to several reasons such as low cost, easy production, strength, etc. There are different grades of steel available according to their properties. Galvanised steel and stainless steel are two types of steel. Galvanised steel is produced from the galvanization of steel. Stainless steel is a type of steel made by adding chromium to metal alloy. Both these types have a property in common; they do not corrode easily. However, there are many differences between them as well. The main difference between galvanised steel and stainless steel is that galvanized steel is produced from dipping steel in molten zinc whereas stainless steel is made by mixing molten steel with molten chromium.

Key Areas Covered

1. What is Galvanised Steel
      – Definition, Composition, and Properties
2. What is Stainless Steel
      – Definition, Composition, and Properties
3. What is the Difference Between Galvanised Steel and Stainless Steel
      – Comparison of Key Differences

Key Terms: Chromium, Galvanization, Galvanised Steel, Metal Alloy, Stainless Steel, Steel, Zinc

What is Galvanised Steel

Galvanised steel is a form of steel made by dipping steel in molten zinc. This is called galvanization. In the galvanization process, a coating of zinc is applied on the surface of steel or iron in order to protect it from rusting. Here, the most common and easiest way is to dip the steel product in a bath of molten zinc. This is called hot-dip galvanizing.

This zinc coating protects the surface of the steel by covering it. Even if a little area of this coating is removed, the opened area is protected by zinc acting as an anode. Here, zinc is oxidized instead of steel, so that rusting is prevented. Therefore, zinc acts as a sacrificial anode and corrosion occur in zinc.

Figure 1: Galvanised steel is used for many purposes since it is cheap.

Sometimes, the galvanizing is done by electro-galvanizing. This is done by immersing the steel in a suitable electrolyte solution along with a zinc electrode. However, galvanised steel is not that strong. But it is cheap since simple methods are used in the process of galvanizing. The zinc covering is only about 1 millimeter thick. Therefore, if there is a scratch in a large area, rusting may start immediately.

What is Stainless Steel

Stainless steel is a form of steel that is made by the mixing of molten steel with molten chromium. The minimum amount of chromium that is added to this metal alloy is 10%. This mixing is done to prevent the steel from rusting.

Since two metals are mixed together, stainless steel is very strong. But it is expensive when compared to other types of steel. In order to mix the two metals, it is essential that the metals should be in the molten state. Otherwise, a uniform mixing would not occur. Then steel is left to cool and harden. Later, the surface of the stainless steel is washed with an acid in order to remove any impurity.

Figure 2: Stainless Steel

Stainless steel does not undergo rusting even if it’s scratched since chromium is present all over the steel, not only on the surface. Stainless steel has high resistant to corrosion by air under normal temperature and pressure conditions. It is even resistant to corrosion by some acids.

Difference Between Galvanised Steel and Stainless Steel

Definition

Galvanised Steel: Galvanised steel is a form of steel made by dipping steel in molten zinc.

Stainless Steel: Stainless steel is a form of steel made by the mixing of molten steel with molten chromium.

Type of Protection

Galvanised Steel: Galvanised steel is covered with a zinc coating to protect steel from rusting.

Stainless Steel: Stainless steel is composed of chromium to provide protection against rust.

Strength

Galvanised Steel: Galvanised steel is not very strong.

Stainless Steel: Stainless steel is highly strong.

Cost

Galvanised Steel: Galvanised steel is less expensive.

Stainless Steel: Stainless steel is highly expensive.

Degree of Protection

Galvanised Steel: Galvanised steel is protected until the zinc coating is present on the surface of the steel. When a scratch occurs on the coating, it starts to corrode.

Stainless Steel: Stainless steel is protected even if there is a scratch on the surface.

Conclusion

Galvanised steel and stainless steel are two types of steel that are made to resist corrosion. Although the purpose of production is the same, there are several differences between galvanised steel and stainless steel due to the difference between the methods of production. The basic difference between galvanised steel and stainless steel can be given as:  galvanized steel is produced from dipping steel in molten zinc whereas stainless steel is made by mixing molten steel with molten chromium.

References:

1. “Galvanization.” Wikipedia, Wikimedia Foundation, 20 Sept. 2017, Available here. Accessed 25 Sept. 2017.
2. “Stainless steel types.” Global | Outokumpu, Available here. Accessed 25 Sept. 2017.
3. “Stainless steel.” Wikipedia, Wikimedia Foundation, 19 Sept. 2017, Available here. Accessed 25 Sept. 2017.

Image Courtesy:

1. “Lots of galvanised steel here – geograph.org.uk – 797130” By Steve F (CC BY-SA 2.0) via Wikimedia Commons
2. “Stainless Steel Sheet Plate Strip Coil Circle” By Jatinsanghvi – Own work (CC BY-SA 3.0) via Wikimedia Commons