Tag Archives: Coated Steel

Differences between various Coated Steel Products

The most versatile, recyclable, environmental friendly metal in world – Steel, is an amazing metal. It has answers to all applications, products.

For Steel users, it might be a tough task in getting to know the different coated steel products that are available, their significance and selecting the right product that suits their application the best.

This article is aimed at helping a bit in knowing the differences between various coated steel products and their usage.

Basically there are four types of most commonly used metal based steel coated products

  1. Galvanised (GI)
  2. Galvannealed (GA)
  3. Galvalume (GL)
  4. Galfan (GL)
  5. Aluzinc – Not considered here as its usage is not very high.

The above mentioned designations viz., GI, GA, are normally used as a short form to designate the grades. This nomenclature can be different in different countries.

The basic purpose of coated steel is to prevent corrosion and enhance the surface life of base metal.  Zinc acts as a cathodic protection and prevents the base metal from corroding. Each of these coated steel has its own application, depending on where they are used and to which environment they would be exposed to.

The below table illustrates the basic differences between these metallic coated steel products in a simple way.

Table 1







1 Coating

Zinc on Steel

Zinc on Steel.

Zinc reacts with Iron to form Zinc iron alloy

43.5% Zinc; 55% Aluminium; 1.5% Silicon.

95% Zinc, 5% Aluminium on Steel

2 Coating designation





3 Application

Ducting, roofing

Deep drawn Automobile parts/ outer panels

Metal Buildings/ Roofing

White goods/ some automobile parts

4 Corrosion resistance ( on a scale of 1 to 5)





5 Spangle on surface


No. Matte finish surface



6 Method

Hot dipped continuous or Electrogalvainsed

Annealing after hot dipped galvanising

Hot dipped continuous

Hot dipped continuous

Galfan is the most recent invention of the above.

Galvalume and Galfan are registered and patented trademarks brands and only those manufacturers with license from the brand owners can produce and sell in these brands.

There are different grades within each variety of above products based on

  1. Strength of the Steel
  2. Coating Mass – Amount of coating
  3. Surface protection (Oiling, chemical passivation, organic passivation)
  4. Surface Quality

Coated Steel is normally designated with a combination alpha-numeric characters.  The below example would help identify the grade from such designations.


Coated steel are normally designated as follows

Grade of steel + coating + spangle designation + surface quality + surface treatment.

Just to give an example let us consider the grade,


DX53D – Deep Drawing grade (European Standard).

ZF – Galvannealed

255 – Coating mass

M – Mini spangle

B – “B” type surface Quality

C – Chemical Passivation.

American and European Standards are most commonly used to designate the grades of coated products.

Color coated steel (Pre-painted steel) is normally on base material of GI, GL. They are designated as PPGI and PPGL. Products of GI and GL when sold without color coating or pre-painting, they are referred as “Bare” GI or “Bare GL.

Pre-painted Galvanised iron (PPGI) & Pre-painted Galvalume (PPGL). PPGL is the famous of the two.

There is one more coated product available in market called “Aluzinc” & “Aluminized Steel”.  These are not considered here, as their demand is not significant compared to the other types mentioned here.

Happy Steeling!