Galvanized Carbon Steel Pipe

As a common pipeline material, carbon steel pipe is widely used in various fields. According to the different carbon content, it can be divided into mild steel pipe (C content ≤ 0.25%), medium carbon steel pipe (C content 0.25-0.6%) and high carbon steel pipe (C content> 0.6%).

However, carbon steel pipe has poor corrosion resistance and is easily affected by the external environment and rusted. In order to solve this problem, people invented the galvanizing process. By galvanizing process, carbon steel pipe’s corrosion resistance and service life can be effectively enhanced. Galvanizing can not only improve the corrosion resistance of carbon steel pipes, but also beautify their appearance. Galvanized carbon steel pipes are widely used in construction, machinery, automobiles and other fields.

Concept and process of galvanized carbon steel pipe

Galvanizing refers to immersing the carbon steel pipe in molten zinc liquid or forming a zinc alloy layer on the surface of the carbon steel pipe by electrolysis. In the galvanizing process, the carbon steel pipe is used as the cathode and zinc is used as the anode. The zinc is attached to the surface of the carbon steel pipe through electrolysis to form a dense zinc-iron alloy layer. This zinc-iron alloy layer has good corrosion resistance and oxidation resistance, and can effectively protect the carbon steel pipe from erosion by the external environment. There are two main galvanizing processes: hot-dip galvanizing and electro-galvanizing:

1. Hot-dip galvanizing

Hot-dip galvanizing is to immerse the carbon steel pipe in molten zinc liquid to form a zinc-iron alloy layer through zinc-iron reaction.

2. Electro-galvanizing

Electro-galvanizing is to deposit a layer of pure zinc on the surface of the carbon steel pipe by electrolysis.

The simplest 3-step method for galvanized carbon steel pipe processing

1. Preliminary preparation

First, the carbon steel pipe needs to be thoroughly cleaned to remove oil, rust and oxides on the surface to ensure that the surface of the steel pipe is clean and free of impurities. The quality of pretreatment directly affects the bonding strength of the zinc layer. It is necessary to use a special cleaning agent with neutral pH, and cooperate with sandblasting or wire brushing to ensure that the substrate meets the Sa2.5 cleaning standard.

2. Galvanizing treatment

The pretreated steel pipe is immersed in a zinc molten pool at 450-460℃ to form a multi-layer protective structure through iron-zinc alloy reaction. The galvanizing time (usually 3-10 minutes) and lifting speed (1.5-2.5m/min) need to be precisely controlled to ensure that the zinc layer thickness is uniform and meets the international standard requirements of 65-300μm.

3. Post-inspection

The last step is post-inspection. After the galvanizing is completed, the galvanized pipe needs to be fully inspected for quality, including the thickness, uniformity and adhesion of the zinc layer. This step is a key link to ensure the quality of the galvanized pipe. Only galvanized pipes that meet the ASTM A123 standard can be put into engineering applications.

Advantages of galvanized carbon steel pipes

1. Improve corrosion resistance

The galvanized layer can effectively isolate the carbon steel pipe from the external environment, thereby preventing corrosion and rust.

2. Beautify the appearance

The surface of the galvanized carbon steel pipe presents a silvery-white luster, which is beautiful and generous.

3. Enhance mechanical properties

The galvanized layer forms a good combination with the carbon steel pipe matrix, which can improve the tensile strength and ductility of the carbon steel pipe.

‌Disadvantages of galvanized carbon steel pipes‌

‌1. Sensitive to mechanical damage‌

The coating is easily scratched during transportation or construction, and the damaged area will accelerate the corrosion of the substrate. The cold-dip galvanized layer has weak adhesion and is more likely to fall off‌.

2. ‌Environmental constraints‌

The hot-dip galvanizing process consumes a lot of energy, and each ton of steel consumes about 40-50kW·h of electricity. The cost of galvanizing wastewater treatment is high‌.

3. ‌Special scene restrictions‌

The fire resistance is poor, and the zinc layer will melt and fail in a fire; long-term contact with acid and alkali media will shorten the service life‌.

Application areas of galvanized carbon steel pipes

Galvanized carbon steel pipes not only have excellent corrosion resistance, but also have good mechanical properties and processing properties. It can operate stably for a long time in harsh environments such as high temperature, high pressure, and humidity, so it is widely used in construction, chemical, petroleum and other fields:

1. Construction field

In the construction field, galvanized carbon steel pipes are often used in indoor and outdoor water supply, drainage, fire protection and other pipeline systems.

2. Chemical and petroleum fields

In the chemical and petroleum fields, galvanized carbon steel pipes are used to transport various corrosive media.

3. New energy fields

In the new energy field, galvanized carbon steel pipes can be used in the pipeline systems of clean energy equipment such as solar energy and wind energy.

4. Environmental protection field

In the environmental protection field, galvanized carbon steel pipes can be used in the pipeline systems of environmental protection facilities such as sewage treatment and exhaust gas emissions.

Summary

In short, carbon steel pipe galvanizing, as an important metal anti-corrosion technology, plays an important role in various fields. With the continuous advancement of science and technology and the continuous expansion of application fields, galvanized carbon steel pipes will play a more important role in the future.