​Longitudinal Seam Welded Galvanized Steel Pipe (LSAW/ERW)

• ​Introduction

Galvanized steel pipe is a type of steel pipe that has been coated with a layer of zinc to prevent corrosion. This coating acts as a barrier, protecting the underlying steel from environmental factors such as moisture, oxygen, and chemicals, thereby extending the pipe’s service life significantly. It is widely used in various industries due to its excellent combination of durability, affordability, and corrosion resistance.

• ​Main Functions

Corrosion Protection: The zinc coating undergoes a chemical reaction to form a passive film, preventing the steel base from rusting and deteriorating.

Structural Support: It provides strong mechanical strength, making it suitable for applications requiring load-bearing or structural stability, such as in construction frameworks.

Fluid Conveyance: Commonly used to transport water, gas, oil, and other fluids, thanks to its smooth inner surface and leak-resistant properties.

Cost-Effectiveness: Compared to other corrosion-resistant materials, it offers a lower cost while maintaining reliable performance.

• ​Tubing Standards

ASTM A53，ASTM A106；

EN 10255，EN 10240；

GB/T 3091，GB/T 13793，GB/T 9711，GB/T 8163.

• ​Material & Performance

Base Material:

ASTM A53: Grade A、B，ASTM A106: Grade A、B、C； EN 10255: S195T、S235JRH、S275JRH、S355JRH； GB/T 3091: Q215A/B、Q235A/B、Q355B, GB/T 8163：10#，20#，Q355，Q420， GB/T 13793: Q195、Q215A/B、Q235A/B、Q355B、Q390B；

Zinc coating:

Hot-dip galvanizing coating – Formed by immersing cleaned steel pipes in a molten zinc bath (temperature ~450°C). The high temperature triggers a chemical reaction between iron (from the steel) and zinc, forming a multi-layer structure.

Thickness – Typically 35~200μm, with thicker coatings for harsher environments (e.g., coastal areas with high salinity).

Performance :

Corrosion Resistance – The zinc coating protects the steel from rust and extends its service life. High Strength – Maintains structural integrity under high pressure and mechanical stress. Versatility – Suitable for water supply, gas transportation, scaffolding, fencing, and more.

• ​Manufacturing Process

Steel Pipe Formation：Produced via seamless or welded (ERW, LSAW) methods.

Surface Preparation: The steel pipe is cleaned to remove rust, oil, and debris through processes like pickling (using hydrochloric or sulfuric acid) and rinsing.

Fluxing: The cleaned pipe is dipped in a flux solution (e.g., zinc ammonium chloride) to prevent re-oxidation of the steel surface before galvanizing.

Hot-Dip Galvanizing: The pipe is immersed in a molten zinc bath (temperature around 450°C), where the zinc reacts with the steel to form a zinc-iron alloy layer, followed by a pure zinc layer on top.

Post-Treatment： Cooling – Remove galvanized pipes from the zinc bath and immediately cool them with cold water spraying or immersion to rapidly solidify the zinc layer, reducing uneven thickness caused by zinc flow. Zinc Layer Trimming – Remove excess zinc nodules and dross from pipe ends and inner walls using mechanical brushing to ensure dimensional accuracy and smooth inner walls.

Quality Inspection: Check zinc layer thickness (with a magnetic thickness gauge), uniformity (inspecting for bare spots or bubbles), and adhesion (using cross-cut or bending tests). Unqualified products are reprocessed.

• Specifications