The production of galvanized ERW pipe involves two main stages: the formation of the pipe using electric resistance welding and the application of a protective zinc coating through galvanization. Each stage is critical to ensuring the final product offers both structural integrity and long-lasting corrosion resistance. Below is a breakdown of the process.
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Step 1: ERW Pipe Formation
Steel coils are continuously formed and welded using high-frequency electric resistance welding (ERW), which ensures:
High production efficiency
Uniform weld quality
Strong mechanical performance due to post-weld annealing and consistent composition between the weld and base metal
Step 2: Galvanization
Hot-Dip Galvanizing (HDG): The welded pipe is submerged in molten zinc at approximately 450°C, forming a thick zinc coating (typically 50–150 μm). This method offers excellent corrosion resistance and is ideal for outdoor or harsh environments.
Electro-Galvanizing (EG): Zinc is applied via electrolysis, creating a thinner (5–20 μm) but smoother and shinier coating. This process is suitable for indoor applications or where only short-term protection is required.
Note:
An excessively thin zinc coating may fail to protect against corrosion, while an overly thick layer can increase internal stresses, leading to peeling or cracking. Therefore, selecting the proper coating thickness involves balancing corrosion protection with processing costs.