Pre-Galvanized Tube Carbon Steel Round Pipe — Factory Direct Supplier | Huaxia-Steel

Pre-galvanized tube (also called factory-galvanized tube, pre-GI tube, or sendzimir-galvanized tube) is a welded round steel tube manufactured from zinc-coated steel strip. The tube is roll-formed and welded from coil that has already been galvanized at the steel mill, which produces a thinner but uniform zinc coating. Pre-galvanized tube is the workhorse of the fencing, HVAC, light structural, and furniture industries. Huaxia-Steel supplies pre-galvanized tube from Chinese mills in a wide dimensional range with light, medium, and heavy zinc coatings.

Product Overview

Pre-galvanized tube begins as cold-rolled low-carbon steel strip that has been continuously hot-dip galvanized at the steel mill (typically Z60 to Z275 coating – equivalent to 20 to 90 microns per side). The strip is then slit to the required width, fed through a series of roll stands to form a round cross-section, and welded longitudinally by high-frequency induction (ERW). The result is a tube that is galvanized on the outside (the inside of the original strip is exposed after forming and welding, but can be re-coated by in-line zinc-rich spray if specified).

Specifications

Item	Details
Type	Pre-galvanized (factory-galvanized) round tube
Standard	EN 10255, ASTM A53 Type E, AS 1074, JIS G3444, GB/T 3091
Outside diameter	15.9 mm – 114.3 mm (1/2 in – 4 in)
Wall thickness	0.7 mm – 4.0 mm (custom up to 6.0 mm)
Length	Standard 6 m fixed; custom 4-12 m fixed
Welding process	High-frequency induction (HFI) ERW
Zinc coating weight	Z60 to Z275 (g/m2, total both sides); custom up to Z600
Surface finish	Spangled zinc, smooth, paintable, or chromated
End finish	Plain ends, threaded ends to ISO 7-1 or ANSI B1.20.1, or socket ends

Zinc Coating Weights and Standards

Coating designation	Total zinc per m2 (both sides)	Equivalent thickness	Typical use
Z60	60 g/m2	~8-10 microns	Indoor furniture, light framing
Z120	120 g/m2	~16-20 microns	HVAC duct, general light outdoor
Z180	180 g/m2	~25 microns	Fencing, light structural
Z275	275 g/m2	~35-40 microns	Outdoor structural, water pipe, agricultural
Z450 (custom)	450 g/m2	~60 microns	Coastal and high-corrosion environments
Z600 (custom)	600 g/m2	~80 microns	Heavy outdoor, industrial atmosphere

The EN 10346 standard covers the strip coating; tube standards (EN 10255, GB/T 3091) reference the coating weight rather than re-measuring on the tube.

Manufacturing Standards

EN 10346 (continuously hot-dip coated steel flat products – covers the strip feedstock).
EN 10255 (non-alloy steel tubes for welding and threading – light gauge).
ASTM A53 Type E (electric-resistance-welded steel pipe, also covers pre-galvanized supply).
AS/NZS 1074 (steel tubes and tubulars for ordinary service).
JIS G3444 (carbon steel tubes for general structural purposes).
GB/T 3091 (welded steel pipes for low-pressure liquid delivery).

Applications

Chain-link and weld-mesh fencing frames, posts, and rails
HVAC ductwork and air-handling pipe
Greenhouse structural frames and agricultural equipment
Light structural framing for sheds, carports, and warehouses
Furniture frames, storage racks, and shop fittings
Water and low-pressure irrigation lines (medium and heavy coating)
Conduit (mechanical protection) for electrical wiring
Automotive components, exhaust tube, and trailer frames
Solar mounting structures (with heavy coating or additional paint)

Pre-Galvanized vs Hot-Dip Galvanized Tube

Attribute	Pre-galvanized tube	Post-galvanized (hot-dip batch) tube
Coating source	Mill-applied on the strip, before forming	Applied on the finished tube after welding
Typical coating weight	Z60 to Z275 (20-90 microns)	45-85 microns typical (batch HDG)
Inside coating	Not by default; can be added via internal spray	Full inside coverage from immersion
Surface finish	Smooth, uniform	Spangled, may vary by region of tube
Cut-end protection	None (cutting exposes raw steel)	Full (batch dips the ends too)
Cost	Lower – efficient strip-based process	Higher – batch process adds handling
Lead time	Shorter (mill-direct coil)	Longer (batch send-out to galvanizer)
Best for	Mass-produced tube, fencing, light structural	Heavy structural, outdoor service pipe

Quality Assurance

Each shipment of pre-galvanized tube from Huaxia-Steel includes:

Mill certificate per EN 10204 2.2 or 3.1 (3.1 on request for code-stamped projects) showing strip chemistry, mechanical values, and zinc coating weight.
Coating weight test by gravimetric or XRF method, reporting grams per square metre total both sides.
Coating adhesion test by bend or impact on sample.
Dimensional check for OD, wall, length, ovality, and straightness.
Hydrostatic test on request (typical for water pipe duty).
Visual and surface inspection for spangle uniformity, bare spots, and weld seam appearance.

Packing and Shipping

Pre-galvanized tube is bundled in hexagonal packs with steel or plastic strapping, end caps fitted, and each bundle wrapped in woven polypropylene or VCI paper for sea shipping. Each tube is marked with size, wall, length, standard reference, and coating weight. Bundling of smaller tubes maximizes container loading: typically 25-30 tonnes per 20 ft container depending on size and length. FOB, CFR, and CIF delivery from Tianjin, Shanghai, and Qingdao.

Why Buy Pre-Galvanized Tube from Huaxia-Steel?

Factory-direct pricing on Z60 to Z275 coating grades
Wide dimensional range from 1/2 inch to 4 inches, custom to 6 inches
OEM cut-to-length and threading service for distribution customers
High-frequency induction ERW with full weld-line NDT options
Dedicated inventory program for large fencing and HVAC distributors
Consolidated shipment with structural sections and pre-painted coil

Need pre-galvanized tube for a fencing, HVAC, or light structural project? Send the OD, wall, length, coating weight, and quantity. Our team will deliver a complete offer including coating certificate, end-finish options, and FOB/CIF pricing within one working day.