Galvanized pipe: a practical choice for rust-proof transportation

Galvanized pipe is a tubular material made from a carbon steel pipe (seamless or welded) with a zinc coating applied to the inner and outer surfaces via a hot-dip or electroplating process. With the combined advantages of "steel pipe's pressure resistance and zinc layer's rust resistance," it offers lower costs than stainless steel pipe, making it a mainstream pipe material in fields such as building water supply, gas distribution, and municipal engineering, addressing the rust problem of carbon steel pipe.

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I. Definition of Galvanized Pipe

The core structure consists of a "carbon steel base pipe" and a zinc coating. The zinc layer protects the steel pipe from rust by providing sacrificial anodic protection (zinc corrodes preferentially) or forming an oxide film, insulating it from air and moisture. Compared to stainless steel pipe, its cost is only one-third to one-half. Globally, galvanized pipe production accounts for over 25% of all steel pipe production, making it a low-cost, rust-resistant, general-purpose pipe.
II. Classification of Galvanized Pipes (by Process + Base Material)
1. Classification by Galvanizing Process
Hot-dip galvanized pipe (GI pipe): The base pipe is immersed in molten zinc (approximately 450°C). The zinc layer is thick (60-200g/m2) and has strong adhesion. The zinc layer is applied to both the inner and outer surfaces, providing excellent corrosion resistance. It is used for outdoor pipes (such as municipal water pipes and fire pipes) and has a service life of 8-15 years.
Electrogalvanized pipe (EG pipe): The zinc layer is deposited through electrolysis. The zinc layer is thin (10-50g/m2) and has a smooth surface. It is usually zinc-coated on one side of the inner or outer wall. It is used for indoor low-pressure pipes (such as household appliance drainage pipes and decorative pipes). It requires painting to enhance corrosion resistance.
2. Classification by Base Material Pipe Type
Galvanized welded pipe: Using welded carbon steel pipe as the base material, it offers low cost and large diameters (15-200mm). It is used for building water supply and gas branch pipes and is the mainstream type in the market. Galvanized Seamless Pipe: Based on seamless carbon steel pipe, it offers strong pressure resistance (≤10 MPa) and high precision. It is used in high-pressure applications (such as high-pressure fire protection pipes and industrial low-pressure oil pipes) and is more expensive than galvanized welded pipe.

III. Core Characteristics of Galvanized Pipe

Rust Resistance: Hot-dip galvanized pipe's internal and external zinc layers resist corrosion in outdoor humid, acidic, and alkaline environments, making it maintenance-free for indoor use. Electrogalvanized pipe is suitable for dry environments, and after painting, its corrosion resistance approaches that of galvanized welded pipe.

Cost Advantage: The price is only 1/3-1/2 that of stainless steel pipe, eliminating the need for secondary corrosion protection compared to painted carbon steel pipe, reducing overall construction costs by 25%-35%.

Balanced Pressure Resistance and Workability: Galvanized welded pipe meets low-pressure transmission requirements (≤4 MPa) and can be welded and threaded on-site. Galvanized seamless pipe is suitable for medium- and high-pressure applications, can be cut and bent, and accommodates complex pipeline layouts. Convenient Recycling: The base material is carbon steel pipe, and the zinc layer can be recycled along with the steel. The zinc can be separated and reused during re-refining. The global recycling rate for galvanized pipes exceeds 75%, aligning with the green trend.

IV. Core Applications of Galvanized Pipes

Construction and Municipal Services: Hot-dip galvanized welded pipes are used for building water supply pipes (water pipes entering households), fire protection pipes (connecting to fire hydrants in corridors), and gas manifolds, resisting indoor and outdoor corrosion. Galvanized seamless pipes are used for high-pressure fire protection main pipes, offering stable pressure resistance.

Industry and Manufacturing: Hot-dip galvanized pipes are used for workshop water supply pipes and low-pressure cooling water pipes, resistant to humid workshop environments. Electrogalvanized pipes are used for household appliance drain pipes (such as washing machine drains) and decorative equipment pipes, offering an aesthetically pleasing surface.

Agriculture and People's Livelihoods: Hot-dip galvanized pipes are used for agricultural irrigation pipes (water pipes for fields) and oil pipes for agricultural machinery, resistant to corrosion from rainwater and soil in the fields. Galvanized welded pipes are used for clothes drying racks and furniture support pipes, balancing rust resistance and strength. Transportation and Infrastructure: Hot-dip galvanized pipes are used for the casing of highway guardrail posts and the internal conduit for streetlight poles, resisting corrosion from road dust and rainwater. Galvanized welded pipes are used for temporary construction pipes (such as temporary water supply pipes on construction sites), offering a high cost-effectiveness.
V. Future Trends in Galvanized Pipes
High Corrosion Resistance: Developing zinc-aluminum-magnesium alloy-coated pipes offers 3-4 times greater corrosion resistance than pure zinc pipes, extending their outdoor service life to 20 years. Promoting the use of epoxy resin-coated galvanized pipes for water corrosion resistance and suitability for drinking water transportation.
Lightweight and High Precision: Producing thin-walled galvanized welded pipes (1.2-2mm wall thickness) for decoration and furniture applications, reducing weight by 20%. Improving the dimensional accuracy of galvanized seamless pipes (outer diameter tolerance ±0.1mm) to meet the requirements of precision equipment.
Environmentally Friendly Process Upgrades: Adopting chromium-free passivation technology (replacing traditional chromate passivation) reduces heavy metal emissions. Optimizing the hot-dip galvanizing process reduces zinc consumption, reducing zinc consumption by 10%-15% per ton of galvanized pipe.
Conclusion
Galvanized pipe, with its "low cost and balanced rust protection," has become a practical, rust-resistant pipe material for the construction, municipal administration, and industrial sectors. In the future, through its highly corrosion-resistant coating, lightweight processing, and environmentally friendly process upgrades, it will further consolidate its position in the mid- and low-end rust-resistant transportation market, continue to replace ordinary carbon steel pipe, and adapt to a wider range of scenarios.

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