What Does Galvanized Coating Mean?
Galvanized coating is the application of zinc coating to prevent corrosion or rusting from the steel or iron structure. The application of zinc on a steel structure is a process called ''galvanization.'' This process was first invented and developed in France and England in 1837, in which a sheet of iron or steel was dipped in a molten zinc bath and cooled (a method called "hot dip galvanization").
Corrosionpedia Explains Galvanized Coating
The most common method of applying a galvanized coating is hot dip galvanization; however, there are various other processes that are also used, such as:
- Zinc electroplating – In this method, a steel sheet is dipped into the zinc ion solution and an electric current is passed through it, which uniformly spreads zinc ion solution on the metal sheet.
- Mechanical plating – In this method, zinc powder along with glass beads and a special reducing agent are coated on the metal sheet, which bonds zinc particles on the surface of sheet.
- Sherardizing – In this method, a metal sheet is heated up to a temperature of 752°F (400°C) and passed through zinc powder. At this high temperature, diffusion between zinc and steel molecules occurs.
- Continuous strip galvanizing and galvanized wire – In this method, a metal strip or metal wire is passed through a solution of molten zinc at a high speed of 590 feet (180 meters) per minute in a controlled air pumping. This applies a zinc coat on the metal sheet.
- Zinc metal spray – In this method, a metal sheet is cleaned to Class III level and then zinc powder is sprayed on top of it with the help of a plasma flame gun.
Galvanization is a useful process because steel will ordinarily severely corrode when exposed to the atmosphere without proper remediation. In comparison, zinc is significantly more resistant to the electrochemical redox reactions that must take place for corrosion and rust formation. Therefore, zinc is alloyed to iron to generate cathodic protection. Increased metal life expectancy, lower cost and increased coating life reliability are some key benefits of galvanization.