How to distinguish cold galvanizing from hot galvanizing

1, process difference: hot dip galvanizing is to degrease the workpiece, wash it with acid, soak it in molten zinc for a certain time, and then take it out. Cold galvanizing, also known as electro-galvanizing, uses electrolytic equipment to degrease and pickle the workpiece, puts it into a solution containing zinc salt, and connects it to the negative electrode of electrolytic equipment.

2. Appearance difference: the appearance of electro-zinc plating is smooth and bright, and the electroplating layer of color passivation process is mainly yellow-green, with rich colors. The appearance of hot-dip galvanizing is slightly rough and silvery white compared with electro-galvanizing, and it is easy to produce process ripples and a few drops, especially at one end of the workpiece.

3. Different thickness: The zinc layer of hot dip galvanizing is relatively thick, generally the thickness is above 10um, so it has good corrosion resistance. Although the surface is bright, it is slightly rough and may have zinc flowers. However, the galvanized layer is very thin, only about 3-5 microns thick. Although the surface is smooth, it will turn black and dirty, with good processability and insufficient corrosion resistance.

Extended data:

Precautions:

1. Alkyd paint cannot be directly coated on the surface of cold galvanized paint during construction, otherwise saponification will occur. Cold galvanized coating can not be coated on the surface of insulating old organic polymer coating and rusty coating, otherwise it will have no anti-corrosion effect.

2. Secondly, the zinc powder content in cold galvanized paint is high and easy to precipitate, so it needs to be fully stirred and dispersed before painting. If the construction method of gas spraying is adopted, it is suggested that the thickness of one paint film should be 40~60μm, and the second paint film should be sprayed after the first paint film is dried. Special sealing agent for cold galvanizing should be selected when matching, which can protect the cold galvanized paint coating and improve the coating quality.

3. In addition, the cold galvanized paint should be packed in 30kg printing barrels, and the unopened shelf life is 12 months. The storage environment of cold galvanized coatings should be dry, cool and well ventilated, and avoid high temperature and away from fire sources. Construction personnel must take protective measures and wear corresponding protective articles when working on site to protect themselves from infringement.

Baidu encyclopedia-cold galvanizing

Baidu encyclopedia-hot galvanizing