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Difference between various coated steel products


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Difference between various coated steel products

  1. 1. by Madhusoodhanan Sayeenathan
  2. 2. Why Metal Coated Steel?  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.  The coating protects the surface of the steel from oxidation and it is also used to enhance the appearance of the material.  Each of these coated steel has its own application, depending on where they are used and to which environment they would be exposed to.
  3. 3. Metal Coated Steel Products  Galvanized (GI) – Hot Dipped & Electrogalvanized  Galvannealed(GA)  Galvalume (GL)  Galfan  Aluzinc  Pre-Painted Steel  Tin plate
  4. 4. Metal Coated Steel Products  Only first 4 categories are considered in this presentation, since they are the most widely used coated steel products.  Aluzinc, Pre-painted Steel and Tin plate are not covered in this article.
  5. 5. Differences between coated Steel Products S.No 1 Parameter Galvanized Galvalume Galfan Zinc on Steel Zinc reacts with Iron to form Zn Iron Alloy 43.5%-Zn; 55%- Al ; 1.5% Si 95% Zinc ; 5% - Al Z ZF AZ ZGF/ZA Ducting, roofing Coating Galvaneealed Deep drawn automobile parts/ outer panels Metal Buildings, roofing White goods/some auto parts 3 2 4 5 2 Coating Designation 3 Application 4 Corrosion Resistance ( 1 to 5 scale) 5 Spangle Yes for HDGI No No No 6 Process Hot Dipped/Electro galvanized Hot Dipped Galvanizing followed by Annealing Hot Dipped continuous Hot dipped continous
  6. 6. Trademarks  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
  7. 7. Designation 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 ZF140 MBC DX53D – Deep Drawing grade (European Standard). ZF – Galvannealed 255 – Coating mass M – Mini spangle B – “B” type surface Quality C – Chemical Passivation.
  8. 8. Some Additional Info  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.
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