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Galvanized steel pipe is a type of steel pipe in which a zinc coating is applied to the surface of ordinary carbon steel pipe through the galvanizing process.

This zinc coating acts as a protective barrier, isolating the steel pipe base from the external environment (especially moisture and oxygen), thereby greatly delaying the corrosion and rusting process of the steel pipe. It is a very traditional and widely used type of pipe.

The main advantages of galvanized steel pipes all stem from the zinc coating on their surface:

1. Outstanding corrosion resistance:

This is the most core advantage. The zinc coating provides sacrificial protection for the steel pipe (the principle is described in Part three), making its lifespan several times or even dozens of times longer than that of ordinary black steel pipes (ungalvanized steel pipes) in general atmospheric and humid environments.

2. Long service life:

Thanks to its corrosion resistance, the service life of galvanized steel pipes is very long, usually reaching 20 to 30 years or even longer, depending on the environmental conditions.

3. High cost-effectiveness:

Although the initial purchase cost is higher than that of PVC or black steel pipes, due to its long service life and extremely low maintenance requirements (no need for frequent anti-corrosion painting), its long-term comprehensive cost is very low.

4. High strength and high toughness:

It inherits all the mechanical property advantages of steel, with high strength, capable of withstanding very high pressure and impact, and is not prone to deformation or damage.

5. Easy to inspect and install:

The silver-gray zinc coating surface makes damage (such as scratches) easily detectable by the naked eye, facilitating timely maintenance. Its installation process is the same as that of ordinary steel pipes, and the construction personnel are very familiar with it.

 

3. What is the principle?

The anti-corrosion principle of galvanized steel pipes mainly relies on two aspects:

1.  Principle One: Barrier protection

The zinc layer densely covers the surface of the steel pipe, just like putting on a "protective suit" for the steel pipe, physically isolating corrosive media such as water and oxygen from the steel base, thereby preventing the oxidation (rusting) of the steel.

2. Principle Two: Sacrificial Anode Protection (Electrochemical protection)

This is the more ingenious and core principle of galvanizing technology. Zinc is more chemically active than iron (the main component of steel) (the standard electrode potential of zinc is lower than that of iron). When the zinc coating is damaged and the internal steel substrate is exposed, a "micro-battery" is formed.

• Zinc as the anode:

Zinc with higher activity will be corroded first.

• Steel as the cathode:

Zinc continuously loses electrons and dissolves, thereby protecting the steel substrate serving as the cathode from corrosion.

This process will continue until the zinc coating is completely exhausted, at which point the internal steel will start to rust. Therefore, even if the galvanized layer has small scratches or damages, it can still provide protection for the steel beneath it.

According to the differences in manufacturing processes, galvanized steel pipes are mainly divided into two categories:

1. Hot-dip galvanizing

Process: The thoroughly cleaned black steel pipe is immersed in molten liquid zinc to cause a reaction on its surface to form an alloy layer, and then it is taken out and cooled.

Characteristics: The zinc coating is relatively thick (usually 50-150μm), with strong adhesion and extremely long corrosion resistance and service life. It is the mainstream process for structural pipes and water supply pipes.

2. Electro-galvanizing

Process: Through electrolysis, zinc ions are deposited on the surface of the steel pipe to form a zinc layer.

Characteristics: The zinc coating is relatively thin (usually 5-30μm), with a smooth, uniform and beautiful surface, but its corrosion resistance is far inferior to that of hot-dip galvanizing. It is mostly used in occasions with high aesthetic requirements and weak environmental corrosiveness, such as furniture and electrical components.

• Main applications:

1. Water pipes:In the past, they were widely used for water supply and gas pipelines in buildings (nowadays, new drinking water pipes have mostly been replaced by plastic pipes or stainless steel pipes, but they are still very common in many old buildings and fire sprinkler systems).
2. Structural pipes: Used for outdoor structural components such as scaffolding, guardrails, greenhouse frames, and transmission towers.
3. Conduit: As a protective pipe for wires and cables in electrical engineering.

• Notes:

Not recommended for drinking water: After long-term use, rust and scale may form on the inner wall, affecting water quality, and zinc may react with minerals in the water.

Avoid using it in heating systems: The circulation of hot water will accelerate the corrosion of zinc and iron.

Cutting and welding: Cutting or welding can damage the zinc coating. Anti-corrosion treatment (such as applying zinc-rich paint) is required at the damaged area to restore protection.

In summary, galvanized steel pipes are a type of steel pipe that acquires extremely strong anti-rust capabilities through the galvanizing process. Their core advantages lie in long service life, high strength, and outstanding cost performance. Their protection principle combines two mechanisms: physical barriers and electrochemical sacrificial anodes.

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