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How to distinguish JDG pipe is cold galvanized or hot galvanized

2023-05-08 14:44:07.887


Release time:

2023-05-08

How to distinguish JDG pipe is cold galvanized or hot galvanized

The two ends of the hot-dip galvanized steel pipe have blue ink printing hoops, and the whole body has implementation standards and specifications; There is a zinc needle or a little tumor hanging at one end of the hot-dip galvanized steel pipe, and there is a complete galvanized layer inside and outside, and the appearance is not smooth as cold galvanized; Cold galvanized coating is bright, and the sun into a certain Angle of this light into colorful, cold plated steel pipe holes only at both ends of the zinc layer, and then there is no galvanized layer, cold galvanized domestic steel pipe ends as smooth, absolutely no zinc tumor. Appearance is not enforced by standards.


Hot dip galvanizing, also known as hot dip galvanizing, is a method of dipping steel components into molten zinc liquid to obtain a metal coating.
 

Principle: Hot dip galvanized coating ability is good, dense coating, no organic inclusion. As we all know, the mechanism of resistance to atmospheric corrosion of zinc has mechanical protection and electrochemical protection, in the atmospheric corrosion conditions of zinc layer surface ZnO, Zn(OH)2 and basic zinc carbonate protective film, to a certain extent to slow the corrosion of zinc, this layer of protective film (also known as white rust) is damaged and will form a new film. When the zinc layer is seriously damaged, endangering the iron matrix, zinc will produce electrochemical protection on the matrix, the standard potential of zinc is -0.76V, and the standard potential of iron is -0.44V. When zinc and iron form microbatteries, zinc will be dissolved as the anode, and iron will be protected as the cathode. Obviously, the atmospheric corrosion resistance of hot-dip galvanizing is better than that of electrogalvanizing.
 

The formation process of hot dip galvanized layer is the process of forming an iron-zinc alloy between the iron matrix and the outermost pure zinc layer, the surface of the workpiece formed an iron-zinc alloy layer during hot dip plating, so that the iron and pure zinc layer is well combined, the process can be simply described as: when the iron workpiece is immersed in the molten zinc liquid, the first zinc and α iron (body-centered) solid melt is formed on the interface. This is a crystal formed by the matrix metal iron dissolved with zinc atoms in a solid state, and the two metal atoms are fused, and the gravitational attraction between the atoms is relatively small. Therefore, when zinc reaches saturation in the solid melt, the two elements of zinc and iron atoms diffuse each other, the zinc atoms diffused into (or infiltrated into) the iron matrix migrate in the matrix lattice, and gradually form an alloy with iron, and the iron diffused into the molten zinc liquid forms an intermetallic compound FeZn13 with zinc, which sinks into the bottom of the hot galvanized pot, that is, zinc slag. When the workpiece is removed from the zinc leaching solution, the surface of the pure zinc layer is formed, which is hexagonal crystal. Its iron content is not greater than 0.003%
 

The cold galvanizing process is used to protect the metal from corrosion by using a zinc filler coating, which is applied to the protected surface by any coating method and dried to form a zinc filler coating with a zinc content (up to 95%) in the dry coating. Suitable for repair work (that is, in the course of repair work, only in the place where the protected steel surface is damaged, as long as the surface is repaired, it can be recoated). Cold galvanizing process is used for corrosion protection of various steel products and structures. (Cold galvanizing is electric galvanizing, the amount of galvanizing is very small, only 10-50g/m2, and its own corrosion resistance is much different than hot dip galvanizing. The price of electric galvanizing is relatively cheap.
In fact, the effect of cold galvanizing, at best and anti-embroidery oil equivalent, even worse!! The key parts of the structure stress, be careful, especially the exposed parts!

 

Steel is galvanized on the surface under the condition of cooling, and hot-dip galvanized steel pipe is galvanized on the surface under the condition of hot dipping, its adhesion is very strong, not easy to fall off, although the phenomenon of corrosion of hot-dip galvanized pipe, but in a long period can meet the technical and health requirements
 

1. Uniform coating, thin thickness; The hot coating is thicker and the thickness is not uniform.
 

2. Plating appearance is bright, hot plating color is dark.
 

3. The coating has poor corrosion resistance because it is thin. The hot coating has good corrosion resistance because it is thicker and forms an infiltration layer with the base metal

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