Zinc Coated Steel Pipe

Hot dip galvanized pipe:

Hot dip galvanized pipes are formed by reacting molten metal with an iron substrate to produce an alloy layer, thereby combining the substrate and coating. Hot dip galvanizing is the process of first pickling steel pipes to remove iron oxide from their surface. After pickling, the steel pipes are cleaned in an ammonium chloride or zinc chloride aqueous solution or a mixture of ammonium chloride and zinc chloride aqueous solution, and then sent to the hot dip galvanizing tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life.

The substrate of hot-dip galvanized steel pipes undergoes complex physical and chemical reactions with the molten plating solution, forming a corrosion-resistant and tightly structured zinc iron alloy layer. The alloy layer is integrated with the pure zinc layer and the steel pipe substrate, so its corrosion resistance is strong.

 

Cold galvanized pipe:

Cold galvanized pipes are galvanized by electricity, with a small amount of galvanizing, only 10-50g/m2, and their corrosion resistance is much different from that of hot-dip galvanized pipes. Most legitimate galvanized pipe manufacturers do not use electric galvanizing (cold plating) to ensure quality. Only small enterprises with outdated equipment and small scale use electrogalvanizing, and of course, their prices are relatively cheaper. The Ministry of Construction has officially announced the elimination of outdated cold galvanized pipes and the prohibition of using cold galvanized pipes as water and gas pipes. The galvanized layer of cold galvanized steel pipes is an electroplating layer, which is independently layered with the steel pipe substrate. The zinc layer is relatively thin and simply adheres to the steel pipe substrate, making it easy to fall off. Therefore, its corrosion resistance is poor. In newly built residential buildings, it is prohibited to use cold galvanized steel pipes as water supply pipes.

 

 

Hot dip galvanized steel pipes are widely used in manufacturing industries such as construction, machinery, coal mines, chemicals, electricity, railway vehicles, automotive industry, highways, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, exploration machinery, and greenhouse construction.

Galvanizing can increase the corrosion resistance of steel pipes and extend their service life. Galvanized pipes have a wide range of uses, in addition to being used as pipeline pipes for general low pressure fluids such as water, gas, and oil, they are also used as oil well pipes and oil delivery pipes in the petroleum industry, especially in offshore oil fields, as well as pipes for oil heaters, condensate coolers, coal distillation and washing oil exchangers in chemical coking equipment, as well as pipes for support frames in trestle piles and mining tunnels.

 

Firstly, use a solvent to clean the surface of the steel and remove any organic matter on the surface.

Then use a tool for rust removal (wire brush) to remove loose or tilted scales, rust, welding slag, etc.

Use acid pickling method.

Galvanizing is divided into hot plating and cold plating. Hot plating is less prone to rusting, while cold plating is more prone to rusting.

 

1. Differences in concepts.

Galvanized steel pipe is a welded steel pipe with a hot-dip or electroplated coating on its surface. Stainless steel pipe is a hollow, elongated, circular steel material.

 

2. Different prices.

The price of galvanized steel pipes is cheaper than that of stainless steel pipes, mainly because the materials and treatment processes of the two are different, resulting in different effects.

 

3. Different application ranges.

Hot dip galvanized steel is widely used in manufacturing industries such as construction, machinery, coal mining, chemical engineering, power, etc. Stainless steel pipes are mainly used in industrial transportation pipelines and mechanical structural components such as petroleum, chemical, medical, food, light industry, mechanical instruments, etc. Also used in furniture and kitchenware.

 

1. Appearance of galvanized pipe fittings

The surface of high-quality galvanized pipe fittings should have a complete coating, uniform transition, and no sagging, dripping, or excessive agglomeration on the surface. The surface of the pipe fittings shall not have defects such as missed plating or exposed iron.

 

2. Galvanized layer thickness

The thickness of the zinc layer on galvanized pipes is an important indicator for judging the quality of galvanizing. Generally expressed in m, it can also be expressed as the weight of galvanized layer per square meter (g/m2). Due to the different magnetic and polarizability of zinc and steel, the thickness of the zinc layer can be measured non-destructive using a zinc coating thickness gauge. To determine the weight of the zinc layer, it is necessary to scrape and sample the zinc layer, and use chemical methods such as antimony chloride method for measurement.

 

3. Uniformity of zinc coating

The high-quality galvanized layer has a uniform texture, and there is no leakage or damage after electroplating. Galvanized pipes can be immersed in a certain concentration of copper sulfate solution for a certain number of times and time. If there is no red extract on the surface, it can be considered galvanized. There are no defects such as missed plating or damage after plating on the pipe fittings.

 

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