Fastener surface treatment knowledge recharge: the difference between cold galvanizing and hot galvanizing

Fastener Surface Treatment—The difference between cold galvanizing and hot galvanizing can be analyzed by process and appearance.

First of all, the process difference: cold galvanizing is also called electro-galvanizing. The workpiece is degreased, pickled, and put into a solution containing zinc salt by electrolysis equipment, and connected to the negative electrode of the electrolysis equipment; zinc plate connection is placed on the opposite side of the workpiece. At the positive pole of the electrolysis device, the power is turned on, and a direction of movement of the current from the positive electrode to the negative electrode is used to deposit a layer of zinc on the workpiece.

Hot-dip galvanizing is to remove the oil, pickling, dipping, drying and immersing in the melted zinc solution for a certain period of time.

The difference in appearance: the appearance of electro-galvanized zinc is smooth and bright, and the electroplating layer using the color passivation process is also yellow-green as the main color, which is colorful. The plating layer using the white passivation process is blue-white or white-green, and the white passivation process is slightly colored at a certain angle with sunlight. In the corners of complex workpieces, it is easy to produce "electric burning" to become gray, and the zinc layer in this part is thick. In the corner of the cathode, it is easy to form a current dead angle to produce an undercurrent dark area, and the zinc layer in this area is thin. There is no phenomenon of zinc film and agglomeration in the whole workpiece. The appearance of hot-dip galvanizing is slightly rougher than electro-galvanized, and it is silver-white. The appearance is easy to produce process water lines and a little drop of corn, especially at one end of the workpiece. However, the hot-dip galvanized zinc layer is several times thicker than electrogalvanized, and the corrosion resistance is several times that of electro-galvanized.

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