Steel is a popular material for sheet metal fabrication. Galvanized steel refers to the galvanized treatment on the steel surface. Galvanized steel is not easy to rust due to the protection of zinc. How does the galvanization work and what are the different types of steel galvanization, let’s get into it.
Galvanized steel refers to ordinary carbon construction steel, which can effectively prevent steel corrosion and rust after galvanizing such as electro galvanizing and hot-dip galvanizing, so as to prolong the service life of steel. It is generally used for building exterior walls, such as glass curtain walls, marble curtain walls, and aluminum curtain walls as columns and stress-bearing materials, or for outdoor telecommunications towers, highways, and other open-air buildings
Advantages of Galvanized Steel
Galvanizing the metal can make it corrosion-resistant. Without a protective zinc coating, steel will always be exposed to elements and will be oxidized and corroded faster. In terms of corrosion prevention, galvanized steel is an economical and effective alternative to austenitic stainless steel, aluminum, and other materials.
There are many ways to protect metal by galvanizing. First, it forms a protective coating that separates the metal from its surroundings. The zinc layer prevents water, moisture, and other elements in the air from corroding the steel. If the zinc coating is scratched carelessly, and the scratch is very deep, the metal is exposed and easy to corrode.
When two metals with different electrochemical compositions contact the existing electrolyte, electrical corrosion will occur. According to the atomic structure of two metals, one is the anode and the other is the cathode. The rate of anodic corrosion is faster than its own corrosion, while the rate of cathodic corrosion is slower than its own corrosion. Zinc is used for galvanizing because it acts as an anode when in contact with many different types of metals. Since the zinc coating in contact with the base metal is usually an anode, the corrosivity of the base metal or cathode is slowed down.
1. Hot Dip Galvanizing
As the name suggests, it involves immersing the base metal into the molten pool of zinc. First, the base metal must be mechanically cleaned, chemically cleaned, or both. This ensures a good bond between the base metal and the zinc coating. After cleaning, the matrix metal is dissolved to remove any residual oxides. The matrix metal is then immersed in the heated zinc solution to form a metallurgical bond. The advantages of this method are economy, speed, and complex shape. However, the resulting coating may not be consistent with other galvanizing processes.
Pre galvanizing is very similar to hot-dip galvanizing but is usually carried out on materials that already have a specific shape. One advantage of this method is that large coils can be rapidly galvanized with a more uniform coating than hot-dip galvanizing. The disadvantage is that once the manufacture of pre-galvanized metal is started, there will be exposed uncoated areas. This means that when a long sheet is cut to a smaller size, the edges of the cut metal are exposed.
3. Electro Galvanizing
Electro galvanizing, different from the previous process, electro grinding zinc does not use the molten pool of zinc. Instead, the process uses the current in the electrolyte solution to transfer zinc ions to the matrix metal. The advantages of this method are uniform coating and accurate coating thickness. However, this coating is usually thinner than the zinc coating obtained by the hot-dip galvanizing method, which may lead to reduced corrosion protection.