Galvanizing is an important manufacturing process in the manufacturing of metal workpieces, and it mainly plays an anti-corrosion role in metal workpieces. Galvanizing is generally divided into cold galvanizing and hot dip galvanizing. Cold galvanizing is a new type of electroplating method. Hot dip galvanizing originated in the cold-rolled strip steel industry more than a hundred years ago and is a relatively old method. hot plating method. The difference between cold dip galvanizing and hot dip galvanizing lies in the following 6 aspects.

1. Conceptual differences

Cold galvanizing, also called electro-galvanizing, uses chemical methods to separate zinc alloy into zinc ions, which are already attached to the surface of steel. Electro-galvanizing generally contains very little zinc and can easily fall off in a humid environment.

Hot-dip galvanizing uses the principle of zinc to resist atmospheric corrosion to electrochemically protect steel and other materials. The zinc carbonate protective film on the surface can slow down the rate of zinc corrosion. Even if it is damaged, a zinc film will be formed again.

2. Process differences

Cold galvanizing uses electrolytic equipment to degrease and pickle the workpiece and put it into a solution composed of zinc salts, and connect it to the negative electrode of the electrolytic equipment; place a zinc plate opposite the workpiece and connect it to the positive electrode of the electrolytic equipment, and turn on the power , using the directional movement of current from the positive electrode to the negative electrode, a layer of zinc will be deposited on the workpiece.

Hot-dip galvanizing involves degreasing, pickling, dipping and drying the workpiece, then immersing it in the molten zinc solution for a certain period of time and then lifting it out.

3. Differences in galvanized layer thickness

The thickness of cold galvanized layer is 3μm~15um, generally 4~13g/㎡.

The thickness of hot-dip galvanizing layer is 45μm~300um, generally 30~60g/㎡, and the maximum is 300 g/㎡.

4. Appearance differences

The outer surface of cold-dip galvanizing is relatively smooth and bright. The electroplated layer that undergoes color passivation process will appear yellow-green, and the electroplated layer that undergoes white passivation process will appear bluish-white. Generally, there is only a small amount of zinc layer at both ends of cold-dip galvanized steel pipes. There is no galvanized layer on the inside.

The outer surface of hot-dip galvanizing is rough, dark in color, and generally silvery white. Due to the production process, some water lines and drop marks are produced on the surface, and the surface does not emit light or reflect light. The hot-dip galvanized steel pipe has a complete galvanized layer both on the inside and outside.

5. Differences in uses

Cold galvanizing is generally used for rust prevention of indoor parts, such as chassis bottoms, panels, small-size fasteners, etc.

Hot-dip galvanizing is generally used for steel parts that work outdoors, such as highway fences, power towers, large-size fasteners, etc.

6. Price difference

Cold galvanizing only has a zinc layer on the surface of the workpiece, while hot-dip galvanizing requires galvanizing both the inside and outside of the workpiece. The zinc layer is thicker, so the price of cold galvanizing is lower than that of hot-dip galvanizing.