1. cold plating: it is a process of anticorrosion treatment on the surface of workpiece by electrochemical principle.

2. Hot-dip galvanizing: also known as hot-dip galvanizing, it is a method of immersing steel components in molten zinc to obtain metal coatings.

Second, the principle is different.

1. Cold plating: After degreasing and pickling, the pipe fittings are put into the solution containing zinc salt with electrolytic equipment and connected to the cathode of electrolytic equipment. A zinc plate is placed on the other side of the pipe fitting and connected to the anode of the electrolytic equipment for power supply. Through the directional movement of current from anode to cathode, zinc layer will be deposited on the pipe. Cold-plated pipe fittings are processed first, and then galvanized.

2. Hot plating: When the iron workpiece is immersed in molten zinc, a solid melt (bulk core) of zinc and α iron is first formed on the interface. This is a crystal formed by dissolving zinc atoms in matrix metal iron in solid state. When two metal atoms fuse together, the attraction between them is relatively small.

Therefore, when zinc is saturated in the solid melt, the atoms of zinc and iron diffuse with each other, and the zinc atoms diffused (or infiltrated) into the iron matrix migrate in the matrix lattice and gradually form an alloy with iron.

Extended data:

1. The whole steel surface is protected, and molten zinc can easily and evenly cover the inside of the pipe fitting in the depression or any corner where other coatings are difficult to enter.

2. The hardness of galvanized layer is greater than that of steel. The hardness of the top Eta layer is only 70 DPN, so it is easy to sag due to collision. However, the hardness values of the lower Zeta layer and the delta layer are 179 and 2 1 1 DPN respectively, which are higher than those of iron materials, so the impact resistance and wear resistance are quite good.

3. In the corner area, the zinc layer is often thicker than other places and has good toughness and wear resistance. Other coatings in this corner are often the thinnest, most difficult to construct and most fragile, so they often need maintenance.

4, even due to mechanical damage or other reasons. Cause a small part of that zinc layer to fall off, expose the iron base. At this time, the surrounding zinc layer will play the role of sacrificial anode to protect the steel here from corrosion. Other coatings, on the other hand, will generate rust immediately and spread quickly below the coating, causing the coating to peel off.

5. The consumption of zinc layer in the atmosphere is very slow, which is about117 to118 of the corrosion rate of steel, and it is predictable. Its life is far longer than any other coating.

6. The service life of the coating in a specific environment mainly depends on the thickness of the coating. The thickness of coating is determined by the thickness of steel, that is, the thicker the steel, the thicker the coating will be, so the thick steel parts in the same steel structure must also be coated to ensure a longer life.

7. Because of its beauty, art, or when it is used in a severely corrosive environment, the galvanized layer can be painted with a dual system. As long as the paint system is selected correctly and the construction is easy, its anticorrosion effect is better than that of painting and hot dip galvanizing alone 1.5~2.5 times.

8. Besides hot-dip galvanizing, there are several other ways to protect galvanized steel. Generally speaking, hot dip galvanizing is the most widely used method with the best anticorrosion effect, the best economic benefit.

Baidu encyclopedia-cold galvanizing

Baidu encyclopedia-hot galvanizing