galvanized erw pipe, galvanized welded pipe, gi erw pipe,hot-dip galvanizing vs electro-galvanizing

Introduction to Galvanized ERW pipe

Date:2025-04-28

Galvanized ERW pipe (also known as GI ERW pipe) is a welded steel pipe that undergoes a zinc coating process—either hot-dip galvanizing (HDG) or electro-galvanizing (EG)—based on high-frequency electric resistance welded (ERW) pipe. The zinc coating significantly enhances corrosion resistance and extends the service life of the pipe. Among these methods, hot-dip galvanizing is more prevalent, offering a thicker zinc layer and stronger anti-rust performance.


Continental Steel Co., Ltd is professional carbon steel ERW pipes manufacturer, for more details, please contact:sales@cscsteel-manufacturing.com


Manufacturing Process of Galvanized ERW Pipe

1. ERW Pipe Production
Using high-frequency electric resistance welding (ERW) technology, steel strips (coils) are continuously formed and welded into pipes. This process is known for its high efficiency, low production cost, and strong weld quality.


2. Galvanizing Treatment

Hot-Dip Galvanizing (HDG): The ERW pipes (black pipes) are immersed in molten zinc at approximately 450°C, forming a thick zinc layer (typically 50–150 μm) with excellent corrosion resistance, ideal for outdoor applications.


Electro-Galvanizing (EG): Using electrolysis, a thinner zinc layer (5–20 μm) is deposited. Although the surface is smoother, its corrosion resistance is comparatively weaker, making it more suitable for indoor or short-term use.


It is important to note that an excessively thin zinc layer may fail to provide adequate protection, whereas an overly thick coating can introduce internal stresses, leading to peeling or cracking. Therefore, the selection of zinc layer thickness must balance protection needs and production costs.


Key Features of Galvanized ERW Pipe

Outstanding Corrosion Resistance: The zinc coating isolates the steel from air and moisture, preventing rust and significantly extending service life (hot-dip galvanized pipes can last 20–50 years outdoors).


Cost-Effective: Compared to seamless or stainless steel pipes, galvanized ERW pipes offer a more economical solution for large-scale applications.


High Strength: Retaining the mechanical strength of ERW pipes, they maintain excellent pressure-bearing capability even after galvanizing.


Good Workability: Easy to cut, bend, and weld (with proper zinc reapplication), making construction efficient.


Aesthetic Appeal: The bright, smooth, silvery appearance of the galvanized surface makes them suitable for exposed installations such as guardrails and building frameworks.


Common Specifications of Galvanized ERW Pipe

Outer Diameter: DN15 (1/2") to DN600 (24")

Wall Thickness: 0.8 mm to 10 mm

Material Grades: Q195, Q235, Q345, SPCC, ST37, and other low-carbon steels

Galvanizing Layer Thickness (HDG):

Standard Grade: ≥45 μm

Enhanced Grade: ≥80 μm


Hot-Dip vs. Electro-Galvanized ERW Pipes

Aspect

Hot-Dip Galvanizing (HDG)

Electro-Galvanizing (EG)

Coating Thickness

50–600 μm

5–15 μm

Corrosion Resistance

Excellent, suited for harsh environments

Moderate, suited for mild conditions

Cost

Higher, but more durable

Lower, suitable for short-term protection

Surface Appearance

Rougher with zinc patterns (zinc flowers)

Smoother and more uniform

Typical Applications

Construction, automotive, agriculture, marine

Small components, indoor use


Application Fields of Galvanized ERW Pipe

Thanks to their strong corrosion resistance and cost advantages, galvanized ERW pipes are widely used across both industrial and civil sectors:

Construction: Scaffolding, steel structures, door and window frames, guardrails, drainage systems.


Municipal Projects: Water supply, fire protection, low-pressure gas transmission.


Agriculture: Greenhouse frames, irrigation piping.


Power and Communications: Wire conduits, cable protection pipes (e.g., KBG/JDG tubes).


Automotive Industry: Components such as chassis parts and exhaust systems.


Furniture Industry: Shelving units, table and chair frames.


Conclusion

Galvanized ERW pipes combine the production efficiency of ERW technology with the corrosion protection of galvanization, making them highly versatile for construction, municipal, agricultural, and industrial applications.
Hot-dip galvanized ERW pipes are ideal for outdoor and harsh environments due to their superior corrosion resistance, while electro-galvanized pipes are better suited for indoor or low-corrosion settings.
When selecting galvanized ERW pipes, it is crucial to consider the service environment, expected lifespan, and budget to ensure optimal performance and cost-efficiency.

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