Introduction to Galvanizing Process

Galvanizing refers to a surface treatment technology in which a layer of zinc is plated on the surface of metals, alloys or other materials to achieve effects such as beautification and rust prevention. The two mainly and widely used methods are hot-dip galvanizing and cold galvanizing (electro-galvanizing).

Differences between Hot-dip Galvanizing and Cold Galvanizing (Electro-galvanizing)

1.Different Principles
Hot-dip Galvanizing: The principle is to immerse steel devices into the molten zinc liquid to obtain a metal coating.

Hot-dip galvanizing

Cold - galvanizing: The principle is that the processed steel devices are degreased and pickled first, and then put into a zinc - salt solution. After being connected to electrolytic equipment, a layer of zinc is deposited on the steel devices by using the electrochemical principle.

2. Different Equipment Required Hot - galvanizing: Pickling equipment, bottom - pumping annealing furnace or bell - type annealing furnace. Cold - galvanizing: Electrolytic equipment.

3. Different Properties and Advantages The thickness of the electro - galvanized layer is usually 5 - 15μm, while the hot - dip galvanized layer is generally more than 35μm, and can even be as high as 200μm. Hot - galvanizing: It is durable and has good anti - corrosion performance. The anti - rust thickness of hot - dip galvanizing with standard quality endows it with excellent durability; the coating has strong toughness. The galvanized layer of hot - dip galvanizing forms a unique smelted metal structure, and this metal structure can withstand mechanical damage during transportation and use. Cold - galvanizing: It has better environmental performance. In the vast majority of cold - galvanizing solvents and diluents, there are no highly - toxic organic solvents. Moreover, the cold - galvanizing process also reduces the volatilization of organic solvents and the energy consumption for drying, which is beneficial to environmental protection.

4. Different Applications Hot - galvanizing: Due to its good anti - corrosion performance, hot - dip galvanizing is widely used in power transmission towers, communication towers, railways, highway protection, street lamp poles, marine components, building steel - structure components, substation - affiliated facilities, light industry, etc. Cold - galvanizing: Cold - galvanizing is the main development direction of environmental protection for heavy - duty anti - corrosion coatings. What's the Difference among White - Zinc Plating, Blue - Zinc Plating, Colored - Zinc Plating and Black - Zinc Plating? The color of the hot - dip galvanized coating is silver - white with a light blue - green tone. The color of some after chromate passivation treatment is silver - white with a light rainbow tone. The exact colors can be seen on street light poles and highway guardrails. We often hear about white - zinc plating, blue - zinc plating, colored - zinc plating and black - zinc plating. They all belong to electro - galvanizing. Why do they have different colors and what's the difference among them exactly?

Colored zinc plating

White zinc plating

Blue zinc plating

Black zinc plating

In fact, these differences are caused by the distinctions in the passivation process after galvanizing. Different passivation solutions result in passivation films with different colors, and their corrosion resistance performance will also vary, which is why there are different names for these processes. The color of the galvanized layer is determined by the passivation process, including processes such as silver-white, blue-white, colored (multicolored, army green), and black. Generally, the order of the corrosion resistance of the galvanized layer from strong to weak is: army green passivation > black passivation > colored passivation > blue-white passivation > white passivation.