Hot-dip galvanized welded carbon steel pipes utilize high-quality welded carbon steel pipes as the base material. Through the hot-dip galvanizing process, both the inner and outer surfaces undergo comprehensive anti-corrosion treatment, forming a uniform, dense, and highly adherent zinc coating. This significantly enhances corrosion resistance and extends service life.
While retaining the high dimensional accuracy, stable forming properties, and significant cost advantages of welded steel pipes, this product offers outstanding rust resistance, moisture resistance, and weathering capabilities. It is suitable for diverse outdoor and complex operational environments.

II. Comparison Table of Hot-Dip Galvanized Welded Carbon Steel Pipes and Cold-Dip Galvanized Steel Pipes

Comparison Item	Hot-Dip Galvanized Welded Carbon Steel Pipe	Electro-Galvanized (Cold-Galvanized) Steel Pipe
Galvanizing Process	Entire pipe immersed in molten zinc	Electrochemical deposition
Treatment Temperature	~450 ℃	Room temperature
Zinc Layer Structure	Iron-zinc alloy layer + pure zinc layer	Single zinc layer
Zinc Layer Thickness	40–85 μm (customizable)	5–15 μm
Zinc Layer Adhesion	Very strong, not easy to peel off	Relatively weak
Weld Corrosion Protection	Weld and base material galvanized simultaneously	Weld prone to corrosion
Corrosion Resistance	Strong	Relatively weak
Outdoor Use	Suitable for long-term use	Not recommended
Service Life	20–30 years	3–8 years
Surface Appearance	Silver-gray, slightly rough	Silver-white, relatively shiny
Initial Purchase Cost	Medium	Low
Overall Cost-Performance	High	Relatively low
Typical Applications	Municipal, fire protection, construction, agriculture	Indoor, temporary, decorative uses

Hot-dip galvanized welded carbon steel pipe for corrosion-resistant industrial piping

Seamless and welded carbon steel pipe with durable hot-dip zinc coating

III. Standards for Hot-Dip Galvanized Welded Carbon Steel Pipes

Standard	Description	Applicable Scope
ASTM A53	Standard Specification: Steel Pipe and Pipe Fittings	Suitable for pressure pipelines and general-purpose welded and seamless carbon steel pipes, widely used for water, gas, steam, etc.
ASTM A500	Standard Specification: Structural Steel Pipe	Suitable for welded steel pipes, commonly used in building structures and industrial carbon steel piping applications.
EN 10255	Non-alloy steel welded pipe for pressure applications	European standard, suitable for hot-dip galvanized welded steel pipes in ordinary building structures and municipal engineering.
ISO 65	Standard Specification: Steel Pipes for Fluid Transport	International standard, commonly used in fluid transport systems such as water, air, and oil pipelines.
BS 1387	British Standard: Welded Carbon Steel Pipe for Piping	Suitable for welded carbon steel pipes for water, gas, and other fluid transport, widely used in the UK and Europe.
JIS G3452	Japanese Industrial Standard: General Structural Steel Pipe	Japanese standard, suitable for hot-dip galvanized welded pipes for structural and fluid transport applications.
GB/T 3091	Chinese National Standard: Welded Steel Pipe	Suitable for water, gas, and general industrial carbon steel welded pipes; one of the commonly used domestic standards.

Common Application Areas
Municipal Water Supply and Drainage (ASTM A53, EN 10255)
Building Structures (ASTM A500, GB/T 3091)
Fire Protection Systems (ASTM A53, EN 10255)
Agricultural Irrigation (ISO 65, BS 1387)

Standard Selection Recommendations
Domestic Projects: Prioritize GB/T 3091 or ASTM A53.
International Markets: Commonly use ASTM A53, EN 10255, and ISO 65 to meet international project requirements.
High-Standard Projects: For special anti-corrosion requirements, select ASTM A53 or EN 10255 with customized thicker zinc coatings.

IV. Chemical Composition and Mechanical Properties of Hot-Dip Galvanized Welded Carbon Steel Pipes

i. Chemical Composition Table

Standard	Carbon (C), max	Manganese (Mn)	Phosphorus (P), max	Sulfur (S), max
ASTM A53	≤ 0.26%	0.60% – 0.90%	≤ 0.035%	≤ 0.035%
ASTM A500	≤ 0.26%	0.60% – 0.90%	≤ 0.035%	≤ 0.035%
EN 10255	≤ 0.25%	0.30% – 0.90%	≤ 0.035%	≤ 0.035%
ISO 65	≤ 0.30%	0.60% – 0.90%	≤ 0.030%	≤ 0.030%
BS 1387	≤ 0.26%	0.60% – 0.90%	≤ 0.035%	≤ 0.035%
JIS G3452	≤ 0.30%	0.30% – 1.00%	≤ 0.035%	≤ 0.035%

ii. Mechanical Properties Table

Standard	Tensile Strength (MPa), min	Yield Strength (MPa), min	Elongation (%), min
ASTM A53	≥ 415	≥ 240	≥ 20
ASTM A500	≥ 400	≥ 250	≥ 20
EN 10255	≥ 360	≥ 235	≥ 23
ISO 65	≥ 410	≥ 240	≥ 25
BS 1387	≥ 410	≥ 240	≥ 20
JIS G3452	≥ 400	≥ 235	≥ 20

V. Zinc Coating Thickness and Corrosion Resistance of Hot-Dip Galvanized Welded Carbon Steel Pipes

i. Zinc Coating Thickness and Corrosion Resistance

Zinc Coating Thickness	Corrosion Resistance	Suitable Environment	Typical Applications
40 μm – 50 μm	General corrosion resistance, suitable for most environments	Lightly humid environments and urban construction areas	Municipal pipelines, building facades, ordinary water supply pipes, etc.
50 μm – 70 μm	Medium corrosion resistance, improved anti-corrosion	Moderate corrosion environments, such as coastal areas and outdoor exposure	Roads, bridges, municipal water supply pipelines, outdoor structures, etc.
70 μm – 85 μm	Strong corrosion resistance, relatively durable	Humid and highly corrosive environments, such as industrial zones and coastal areas	Agricultural irrigation, steel structure buildings, outdoor facilities, large public pipelines, etc.
≥ 85 μm	Extremely strong corrosion resistance, high anti-corrosion performance	Extreme corrosive environments, such as coastal, chemical, and marine settings	Oil & chemical plants, offshore platforms, coastal protection, highly corrosive environments, etc.

ii. Relationship Between Zinc Layer Thickness and Corrosion Resistance

Thin Zinc Layer (40–50 μm):
Corrosion Resistance: Suitable for general non-extreme corrosion environments, providing basic anti-corrosion protection.
Applicable Environments: Such as ordinary municipal construction, indoor piping, etc. Not suitable for long-term exposure to high-humidity or high-salinity environments.
Medium Zinc Coating (50–70 μm):
Corrosion Resistance: Suitable for coastal and relatively humid environments, offering extended service life.
Applicable Environments: Building structures, standard municipal water supply/drainage pipelines, outdoor equipment, etc.
Thick Zinc Coating (70–85 μm):
Corrosion Resistance: Provides exceptionally strong corrosion protection, suitable for harsh environments.
Suitable Environments: High-humidity, coastal, chemically contaminated, or heavy salt-fog areas. Suitable for long-term use.
Extra-thick zinc coating (85 μm and above):
Corrosion Resistance: Exceptional corrosion resistance, maintaining durability for extended periods in extreme corrosive environments.
Suitable Environments: Marine engineering, chemical plants, mines, ports, oil and gas industries, and other extreme environments.

VI. Selection Recommendations for Hot-Dip Galvanized Welded Carbon Steel Pipes

Determine the operating environment
Mild corrosion: Select a 40-50 μm zinc coating, suitable for general municipal and construction projects.
Moderate corrosion: Select a 50-70 μm zinc coating, suitable for coastal and humid environments.
Severe corrosion: Select a zinc coating exceeding 70 μm, suitable for chemical plants, ports, offshore platforms, and similar environments.
Select wall thickness based on pressure and load requirements
Low to Medium Pressure: Wall thickness 1.5–4.0 mm.
High-Pressure Systems: Wall thickness ≥4.0 mm.
Select Pipe Dimensions
Outer Diameter: Common sizes DN15–DN600. Choose based on flow requirements and installation space.
Wall Thickness: Select thickness meeting pressure and strength requirements.
Select End Finishes
Welded or Flanged Connections: Choose plain ends or chamfered ends.
Quick Connect: Choose threaded or capped ends.
Confirm Standards
Select based on regional or project standards, e.g., ASTM A53, EN 10255.
Length and Customization
Standard lengths are 6m or 12m, custom lengths available upon request.
Consider Transportation and Packaging
Ensure pipes are adequately protected during transport to prevent damage to the zinc coating.

VII. Inspection Standard Table for Hot-Dip Galvanized Welded Carbon Steel Pipes

Inspection Item	Test Method / Standard Requirements	Applicable Standards	Remarks
Chemical Composition	Spectroscopy or chemical analysis to measure elements such as C, Mn, P, S	ASTM A53, ASTM A500, EN 10255, ISO 65, etc.	Ensure alloy composition of the pipe meets specified requirements
Mechanical Properties	Tensile test: measure tensile strength, yield strength, and elongation	ASTM A53, ASTM A500, EN 10255, ISO 65, etc.	Tested using a universal testing machine
Dimensional Tolerance	Measurement of outside diameter, wall thickness, and length	ASTM A53, EN 10255, ISO 65, JIS G3452, etc.	Measured using calipers or laser distance meter
Zinc Coating Thickness	Measured by magnetic method or weight method	ASTM A123, EN 10255, etc.	Zinc layer thickness should be 40–85 μm to suit different environments
Surface Quality	Visual inspection and hardness test to check zinc adhesion and surface defects	ASTM A53, EN 10255, ISO 65, etc.	Check for scratches, cracks, and other surface defects
Hydrostatic Test	Test for leakage or deformation under specified pressure	ASTM A53, EN 10255, etc.	Ensure the pipe withstands working pressure without leakage
Bending Test	Bend pipe to a specified angle and check bending performance	ASTM A53, EN 10255, etc.	Ensure the pipe can bend without cracking