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How to distinguish between hot-dip galvanized steel and cold-dip galvanized steel?

Feb 08, 2023

First of all, the process difference is:

Hot-dip galvanizing is to immerse the workpiece in the molten zinc solution for a certain period of time after degreasing, pickling, dipping, and drying, and then take it out.

Cold galvanizing is also called electrogalvanizing. It uses electrolytic equipment to put the workpiece into a solution composed of zinc salt after degreasing and pickling, and connects the negative electrode of the electrolytic equipment; a zinc plate is placed on the opposite side of the workpiece and connected to the electrolytic equipment. The positive electrode is connected to the power supply, and a layer of zinc will be deposited on the workpiece by using the directional movement of the current from the positive electrode to the negative electrode.


The difference in appearance:

The appearance of electro-galvanized is relatively smooth and bright, and the electro-plating layer adopting color passivation process is also yellow-green as the main color, which is colorful. The electroplating layer using the white passivation process is bluish white or white with green light, and the plating layer of the white passivation process is slightly colorful when it is at a certain angle to the sunlight. The corners and edges of complex workpieces are prone to "electric burning" and become dark, and the zinc layer is thicker in this part. In the inner corner, it is easy to form a current dead angle and produce an undercurrent gray area, and the zinc layer in this area is relatively thin. The workpiece as a whole has no zinc tumor, agglomeration and other phenomena. The appearance of hot-dip galvanizing is slightly rougher than that of electro-galvanizing, and it is silvery white. The appearance is prone to process water marks and a little dripping, especially at one end of the workpiece. However, the zinc layer of hot-dip galvanizing is dozens of times thicker than that of electro-galvanizing, and its anti-corrosion performance is dozens of times that of electro-galvanizing.


The difference between galvanized products:

1. The inner and outer walls of the hot-dip galvanized steel pipe are galvanized, while the cold-galvanized steel pipe is only galvanized on the outer wall.

2. The cold plating layer is uniform and the thickness is very thin; the hot plating layer is thicker and the thickness is uneven.

3. The appearance of cold plating is bright, while the color of hot plating is darker.

4. The cold plating layer is thinner and has poor corrosion resistance; the hot plating layer is dozens of times thicker than cold galvanizing, and forms an infiltration layer with the base metal, which has good corrosion resistance.

5. The surface of cold-dip galvanized steel pipe looks brighter, smooth and flat; the appearance of hot-dip galvanized steel pipe is not as delicate and bright as that of cold-dip galvanized steel pipe. .


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