May. 27, 2022
Black fittings and galvanized fittings are the two most common types of fittings used to transport liquids and gases. The difference is that galvanized pipe fittings have a zinc coating, while black pipe fittings do not. Therefore, galvanized pipe fittings are more durable. Even some professionals sometimes get confused about where and under what circumstances to use these fittings.
We should first understand the process of galvanizing. Galvanizing is a technique of protecting pipe fittings from corrosion caused by exposure to the atmosphere by adding a protective coating made of zinc. The most common method of galvanizing is hot dip galvanizing.
Hot dip galvanizing is the process of immersing pipe fittings in molten zinc to produce a corrosion-resistant coating of zinc-iron alloy and zinc metal. When the pipe is immersed in zinc, a chemical reaction occurs between the iron in the pipe and the molten zinc, and the coating develops a uniform thickness over the entire pipe.
The color of the black pipe fittings comes from the iron oxide formed by the natural oxidation of the surface during processing. Since it has no anti-corrosion coating on its surface, minerals in the fitting can dissolve into the water, causing blockages. Therefore it is not suitable for the transport of water. The gas will not corrode the fittings, so black fittings are suitable for gas systems.
Galvanized pipe fittings are ideal for conveying water. Galvanizing gives the fittings higher corrosion resistance and helps prevent the build-up of mineral deposits that can clog the pipes. In the past, the workmanship of galvanizing was poor. The zinc coating of galvanized pipe fittings tends to peel off, exposing the fittings to oxygen and water. In this way there is a risk of corrosion of the pipe fittings, eventually leading to gas leakage. In view of this, the transport of gas with galvanized pipe fitting is dangerous, so it is mainly used for transporting water outdoors and in industry.
But now, the process of galvanizing has improved a lot, and the zinc coating will not peel off. As the largest manufacturer of malleable steel pipe fittings in China, We JIANZHI have three surface treatment methods of hot-dip galvanized, cold-galvanized and black parts for customers to choose from according to different needs.
The production of galvanized pipe fittings is more costly than the production of black iron fittings. This is due to the additional galvanizing process used in the production of galvanized pipes. In this case, it is assumed that the 2 pipes are of the same thickness. However, if the black iron pipe fitting is thicker than the usually galvanized pipe fitting (e.g. gas pipe fitting), it will be more expensive, which is one of the reasons of more black fittings are used in the transportation of gas.
Therefore, unless there are local regulations, galvanized pipe fittings can be used in gas systems. So when you want to use galvanized pipe fittings in gas pipelines, please consult local regulations first.
But one thing worth noting: black pipe fittings cannot be mixed with galvanized pipe fittings, especially when connecting pipes installed underground. This is because there will be different metallic or galvanic reactions between black iron and galvanized coatings. But don't worry if installed in the atmosphere, the reaction will usually not be as strong as if installed in soil or water.
If you want to know more about high-quality galvanized pipe fittings, please feel free to contact us.
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