what is the difference between hot galvanized and cold galvanized

Dec 19, 2019
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The difference of process:

Cold galvanizing, also called electrogalvanizing, is the use of electrolytic equipment to degrease and pickle the workpiece into a solution containing a zinc salt, and connect 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. Positive electrode, turn on the power, use the current to move from the positive electrode to the negative electrode, and a layer of zinc will be deposited on the workpiece;

Hot-dip galvanizing is to degrease the workpiece, pickling, dipping, and immersing it in the molten zinc solution for a certain period of time.

The difference in appearance:

The appearance of electrogalvanized is relatively smooth and bright, and the electroplated layer adopting the color passivation process is also yellow-green as the main color, which is colorful. The plating layer using the white passivation process is cyan white or white is green, and the plating layer with the white passivation process is slightly colorful at a certain angle with the sunlight. It is easy to produce "electric burn" at the corners of complex workpieces and become dark. The zinc layer in this part is thick. The dead corner of the current is easy to form at the corner area, and a dark area of undercurrent is generated, and the zinc layer in this area is thin. The whole workpiece is free of zinc knobs and agglomeration.

The appearance of hot-dip galvanizing is slightly rougher than that of electro-galvanizing, and it is silver-white. The appearance is prone to process watermarks and a little dripping, especially at one end of the workpiece.

However, the slightly rough hot-dip galvanized zinc layer is dozens of times thicker than electroplated zinc, and the anti-corrosion performance is also dozens of times that of electrogalvanized. Naturally, the price is also much higher than cold galvanized, but in the long run , Hot-dip galvanizing for more than 10 years will be more popular than cold-dip galvanizing with only 1-2 years of anti-rust effect.