Difference between various coated steel products

Steel is a very versatile material that can be used for almost anything if it has undergone the right treatment. The right coating for your steel product be it tinplated steel, or galvanized steel, GI profile sheet or Galvalume will enhance the longevity and performance of your project. 

The main ingredient that is used to coat steel is Zinc as it offers a cathodic protection. This method uses the idea of a using a corrosive metal that is sacrificed in order to the prevent the main base metal from corroding. In most cases the steel is prevent by coating it with zinc or zinc alloy. 

Different methods of Coating steel

The application of Zinc and zinc alloys takes place on steel in multiple ways. The most common forms are:

Electro Galvanization- this process used an electric current running through a zinc or saline solution with a zinc anode and a steel conductor.

Hot Dipping – This process involves immersing steel in molten zinc at 450°C. Once the steel is removed from the molten zinc bath, the reaction of zinc with the oxygen and CO2 in the air forms a hardened layer.

Different Types of Coated Steel Products

Depending on the environment and application the steel is required for, specific coatings is required. The most popular steel treatments are:

Galvanised Steel (GI)

Galvanised steel is processed by coating steel with zinc. This GI profile sheet is popularly used for roofing and for ducting. This is formed via a ‘hot dipping’ method or through electro galvanisation. GI steel is shiny and fairly resistant to corrosion.

Galvannealed (GA)

Galvannealed steelalso is zinc coating on used primarily for automobile parts like outer panels. The difference between GA and GI steel is that annealing is done after the hot dipped galvanization to form a zinc-iron alloy. This type of steel has a matte finish and is not as resistant to corrosion as GI.

Galvalume (GL)

Galvalume steel is coated with a mixture of zinc, silicon and aluminium. The mixture of the coating is the proportion of 55% aluminium, 43.5% and 1.5% silicon. GL steel is popularly used for roofing and on metal buildings. This is formed through continuous hot dipping method and has a poor surface finish. It is more corrosion resistant as compared to GI and GA and can only be produced by licenced manufacturers due to its patented trade mark. 

Galfan (GL)

This type of coated steel is commonly found in white goods and a few automotive parts. It is coated with 95% zinc and 5% aluminium. This modern product is very resistant to corrosion and like Galvalume is a patented trademark brand.