There are three basic elements to the galvanizing process:

  1. Surface Preparation (Cleaning)
  2. Galvanizing
  3. Inspection (Quality Control)

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:

  1. Caustic Cleaning
    Material is immersed in a hot caustic solution to remove grease, oil, dirt, and water-based paints. Other contaminants that cannot be removed by the normal chemical cleaning procedures include but are not limited to: welding slag, splatter, antisplatter, lacquer and oil-based paints.
  2. Acid Pickling
    Material is immersed in a dilute acid solution to remove all rust, mill scale and any other surface contaminants.
  3. Fluxing
    The material is immersed in a heated aqueous zinc-ammonium chloride solution. This step is performed to remove any remaining impurities, moisture, or oxide film from the iron or steel and to ensure that the metal’s surface is chemically clean and ready for galvanizing. Upon removal from the flux solution, the work is air-dried before entering the molten zinc.
Galvanizing
The work is immersed in molten zinc where it will react to form a series of zinc-iron alloy layers. Immersion time varies according to the thickness and weight of the material being galvanized. The material will be withdrawn from the zinc kettle when the coating thickness meets or exeeds the appropriate minimum coating thickness as specified in the relevant ASTM standard.
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. Following galvanizing, material is weighed, the coating thickness is tested for compliance with ASTM standards, and the surface quality of the material is visually inspected. If necessary, the material is cleaned to remove excess zinc drips and runs. The primary objective of galvanizing is corrosion protection, which is far superior to painting.
ZINC COATING

Zinc protects the steel in 2 ways. The first is by barrier protection. Zinc provides a tough metallurgical bonded zinc coating, which completely covers the steel and seals it from the environment.

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GALVANIZING PERFORMANCE

For over 250 years, hot-dip galvanizing has proven to be a high quality and cost effective corrosion protection coating. In most applications hot-dip galvanizing is superior to paint.

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