Galvanized Round Pipe

Hot-dip galvanized round pipes offer excellent corrosion resistance and a long service life, suitable for outdoor applications, fire sprinklers, municipal water supply, gas transmission, buried pipelines, and corrosive coastal and industrial environments, making them the preferred material for main pipelines in engineering projects. Cold-dip galvanized round pipes have a smooth surface, high precision, and moderate cost, and are often used in dry, non-corrosive environments such as indoor wiring, low-pressure plumbing, decorative structures, and lightweight supports, meeting the needs of indoor lightweight piping.

What are the service lives of hot-dip galvanized and cold-dip galvanized round pipes?

What is the typical zinc coating thickness of hot-dip galvanized round pipes?

Mainly classified according to steel pipe wall thickness requirements:

I. National Standard (GB/T 13912-2002) Zinc Coating Thickness

Classified by steel pipe base material thickness:

Wall thickness ≥ 6mm (thick-walled pipes above DN100)

Average zinc coating ≥ 85μm

Local (single point) ≥ 70μm

3mm < Wall thickness < 6mm (DN50～DN80)

Average ≥ 70μm

Local ≥ 55μm

1.5mm ≤ Wall thickness ≤ 3mm (DN15～DN40)

Average ≥ 55μm

Local ≥ 45μm

II. Common Requirements for Fluid Pipes (GB/T 3091-2025)

Total weight of zinc coating on inner and outer surfaces ≥ 300g/㎡

Equivalent thickness approximately ≥ 42μm (minimum requirement for foundation)

Common high standards for engineering / fire protection / water supply:

Zinc coating weight ≥ 500g/㎡ → Thickness approximately ≥70μm

Industry standard: Average ≥85μm, locally ≥70μm

III. Market standard values

Hot-dip galvanized round pipe for general engineering:

Average 70～100μm, locally ≥55μm

High standard for fire protection/municipal/outdoor use:

Average ≥85μm, locally ≥70μm

Cold-dip galvanized (electro-galvanized) round pipe:

Only 5～20μm (far lower than hot-dip galvanizing, unsuitable for outdoor use)