03 Mar

Malleable iron fittings are widely used in automatic sprinkler system in fire engineering, but there are many kinds, how to know?

Steel pipes, made of iron, are prone to rust when exposed to air. In particular, our steel pipe fittings are mainly used for fire protection and water supply engineering, pipe fittings exposed to damp environment for a long time, more prone to corrosion. So malleable iron pipe needs to do anti-rust treatment on its surface. The surface anti-rust treatment of Ma steel pipe fittings is generally divided into hot-dip galvanizing and cold galvanizing. Hot-dip galvanizing is a galvanizing process in which the pipe is immersed in the molten zinc solution at 700-800 °C to cover the surface of the pipe with a layer of zinc. Cold galvanizing is also called galvanizing, its principle is to rely on electrophoresis phenomenon, will be hung in the anode zinc transfer attached to the cathode hanging on the surface of the pipe, and then form a thin and uniform zinc layer.

Hot-dip galvanizing is an effective metal corrosion protection method, mainly used in various industries of metal structure facilities. The utility model is to immerse the steel parts after rust removal into the molten zinc liquid at about 500 °C, so that the surface of the steel members is attached with a zinc layer, thereby playing the purpose of corrosion protection. Hot dip galvanizing process: finished pickling - washing - add plating solution - drying - hanging plating - cooling - medicine - cleaning - grinding - hot galvanizing completion. Hot-dip galvanizing is developed from the older hot-dip galvanization method. It has been used in industry for more than 170 years since 1836 in France. In the past thirty years, with the rapid development of cold rolled strip, hot-dip galvanizing industry has developed on a large scale.

The cost of hot-dip galvanizing is higher than cold galvanizing, but hot galvanizing because the galvanizing layer is thicker, Moreover, the surface zinc layer reacts with the iron matrix at high temperature, resulting in a transition layer between the zinc layer and the iron substrate, so the combination of zinc layer with the tube matrix is particularly firm and not easy to fall off. Although the cost of cold galvanizing is relatively low, the zinc layer is uniform and good-looking, but because electroplating is only covered with a layer of zinc metal film on the surface of the pipe substrate, the galvanized layer is thin and easy to fall off. In addition, a large amount of toxic waste liquid is produced in the process of zinc electroplating.

Because the malleable iron pipe is connected by a thread, it can also be called a thread pipe. However, it should be noted that although the majority of galvanized pipe fittings refer to malleable iron pipe fittings, but because some welded pipe fittings or other iron pipe fittings also do galvanizing treatment on the surface, so, strictly speaking, galvanizing pipe fittings does not equal malleable iron pipe fittings.

The same is true of threaded pipe fittings. Some iron pipes and even plastic pipes are also threaded, but the material is not malleable iron. Similarly, in the strict sense, the thread fittings are not equivalent to the malleable iron pipe fittings.

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