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The Galvanizing Process There are three basic elements to the galvanizing process.
Surface Preparation Surface preparation is the most critical in the galvanizing process. If the steel is not properly cleaned the zinc will not adhere to the steel. The three primary steps for surface preparation are:
Caustic Cleaning - The metal is first immersed into a hot alkali solution to remove dirt, grease and oil from the metal surface. Acid Pickling - The metal is immersed into a acid solution to remove the scale and rust. Fluxing - In the last step the metal is immersed in a flux solution consisting of Zinc Ammonia Chloride. The flux removes oxides and prevent further oxides from forming on the surface of the metal prior to galvanizing. The flux also promotes bonding of the zinc to the steel. Galvanizing In this step the steel is completely immersed in 99.9% molten zinc. The zinc bath temperature is maintained at about 830 degrees Fahrenheit. The steel items are immersed long enough to reach bath temperature at 830 degrees. The articles are slowly withdrawn and any excess zinc is removed by draining and wiping. Inspection and Quality Control The most important method of inspection for galvanized steel is the thickness of the zinc. Other things to consider would be uniformity of the coating, adherence of the coating and appearance. The primary objective of galvanizing is corrosion protection, which is far superior to painting. |
