Blog 5 Steel - Finishes & Surface Treatment

A documentary[1], dating to the time of World War II, Ohio.    

The process of steelmaking, from the assembling of the raw materials to the final rolling process, can be seen in the sharp black and white video. To watch something that is new to the eyes was 

Steel as a usable material goes through a lot of processes, for us to have the steel what we see in our daily life; from finishings and heat treatments to surface treatments depending upon its intended use. 

Heat treatment  

After rolling, the steel material which has already been cast and rolled into the required forms, steel is heat-treated to improve its strength, hardness, and ductility. 

Quenching 

  • The steel is heated and cooled suddenly in water or oil bath
  • A crystal-like layer is formed.
  • The process protects the steel from the effects due to exposure to the atmosphere.

Tempering 

  • To increase the strength, hardness, and ductility
  • The steel is heated in a controlled manner and then cooled down

Annealing -

  • The steel is heated and cooled down in the same furnace
  • Heating and cooling processes are done very slowly, to make the hard steel soft.

Galvanization 

  • Application of Zinc coating to prevent rusting.
  • Two methods of zinc coating are:

Hot dipped 

  • Immersing the metal in a bath of molten zinc layer of 1700 F
  • Repeated to get the required coating thickness.
  • In certain cases, the corrugation is formed on the metal surface before heating.
  • Outcome - Easier to make, cheaper and large size production

Cold dipped 

  • The zinc layer is electrically coated on the metal.
  • The result is a steel with a shiny surface.
  • The metal will be less durable than that of hot-dipped metal.
  • Outcome - Harder to work with, lesser in strength in compared to hot-rolled steel. 

Metal Surface Treatments 

For metals like steel to satisfy the requirements and needs in the architecture and construction industry, certain sets of surface treatments are necessary depending upon the intended use.

  • Polishing - To render a perfect and smooth look on the metal surface.
  • Brushing- This process is to render a textured and smooth finish using brushes
  • Electropolishing - Treating the metal in an electrochemical solution to get a corrosive resistant and bright appearance. 
  • Electrolytic coloring - Dyeing the surface with metal salts
  • Burnishing - Surface treatment to make the metal look shinier. 
  • Acid Etching - The metal surface is covered with a specific material, leaving open certain areas. The exposed surface is etched for aesthetic appeal
  • Painting -  The metal surface is painted for preferably aesthetic purposes. 
  • Enameling - Coating layer(s) of enamel to improve the fire resistance of the metal
  • Physical vapor deposition - Applying a color- metal coating on the surface of the steel mostly for aesthetic purposes.
  • Metallic coating - It is one of the ways of corrosion treatment. 

Fire protection - Steel

Steel is a metal sensitive to the temperature changes in the atmosphere.

Enclosing the metal with a gypsum layer, protecting from the exposure of the environment are some methods to fire-protect steel.

Here comes our hero, Stainless steel the most elite and strong product of steelmaking, and has the best of properties of any variety of steel, also not to forget its fire-resistive character.


- Janani Venkateswaran


Location: India

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