The appearance of cold galvanizing is smooth, bright, uniform and even. The electroplating layer with color passivation process is also yellow-green, showing seven colors. The white passivation coating is blue-white or green, while the white passivation coating is slightly colorful from a certain angle to the sunlight. There are only a few zinc layers on both ends of the cold-dipped steel pipe, and no zinc layers on both ends of the cold-dipped steel pipe. The two ends of the cold-dipped galvanized steel pipe are as smooth as before, and there are absolutely no galvanizing tumors, and the appearance of the steel pipe does not comply with the specifications.
It occurs simply at the corner and edge of the disordered workpiece, and becomes dim by electric firing, where the zinc layer is thicker. It is easy to form a dead angle of current at the pudendal corner and produce a dark area of undercurrent, where the zinc layer is thinner. There are no zinc nodules and caking on the whole workpiece.
Compared with cold galvanizing, the appearance of hot galvanizing is darker, slightly rough, no smooth galvanizing, silvery white, simple process water marks and a few droplets, especially at one end of the workpiece, and the appearance is not bright and not reflective. Hot-dip galvanized steel pipes have blue ink stamped hoops at both ends, and all of them have specifications and specifications. At one end of the hot-dip galvanized steel pipe, there are zinc needles or a few tumors hanging, both inside and outside have good galvanized layer.
In a word, the zinc layer of hot galvanizing is tens of times thicker than that of cold galvanizing, and its corrosion resistance is also tens of times that of cold galvanizing.
At present, many enterprises choose steel grille, grille, steel grille products for the construction of platform pedals, ceiling and other projects in the factory. According to different projects, customers have different requirements for product quality, especially for galvanizing quality.
Principle: Hot-dip galvanizing has good covering ability, compact coating and no organic adulteration. It is well known that the anti-atmospheric corrosion mechanism of zinc is mechanical maintenance and electrochemical maintenance. Under atmospheric corrosion conditions, zinc coating has zinc oxide, zinc (OH) 2 and basic zinc carbonate maintenance film on its surface, which to a certain extent slows down the corrosion of zinc. This maintenance film (also known as white rust) will be damaged and form a new film. When zinc layer is destroyed severely and iron matrix is endangered, zinc maintains electrochemically. The standard potential of zinc is -0.76V, the standard potential of iron is -0.44V. When zinc and iron form micro-battery, zinc is dissolved as anode and iron as cathode is maintained. The atmospheric corrosion resistance of hot-dip galvanizing to base metal iron is better than that of galvanizing.
The formation process of hot dip galvanizing layer is the process of forming iron-zinc alloy between iron base and the outermost pure zinc layer. The iron-zinc alloy layer is formed on the surface of the workpiece during hot dip galvanizing, which makes the iron and pure zinc layer combine well. The process can be simply described as: when the iron workpiece is immersed in molten zinc solution, the first solid melt of zinc and alpha iron (core) is formed on the interface. This is a kind of crystal formed by the dissolution of zinc atoms in the solid state of the matrix metal iron. The two metal atoms are fused, and the attraction between the atoms is relatively small. Therefore, when zinc saturates in the solid melt, the two elements of zinc and iron disperse each other, and the zinc atoms disperse into (or enter) the iron matrix move in the lattice of the matrix, and gradually form alloys with iron, while the iron dispersed in the molten zinc liquid forms the intermetallic compound FeZn13 with zinc, and sinks into the bottom of the hot-dip galvanizing pot, that is, zinc slag. When the workpiece is removed from the zinc dipping solution, the surface of the workpiece forms a pure zinc layer, which is a hexagonal crystal. Its iron content is not greater than
Cold galvanizing process is used to protect metals from corrosion. For this reason, zinc filler coatings are used, which are coated on the maintained surface by any coating method. After drying, zinc filler coatings are formed, which contain zinc (up to 95%) in the drying coatings. Suitable for repairing operation (that is, in the process of repairing operation, only in the locality where the surface of the steel is damaged by maintenance, as long as the surface is repaired, it can be re-coated). Cold galvanizing process is used for corrosion protection of various steel products and structures. (Cold galvanizing is galvanizing, the amount of galvanizing is very small, only 10-50g/m2, its corrosion resistance is much different than hot dip galvanizing. The price of galvanizing is relatively cheap.
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