Zinc- coated Rectangular Steel Tube - High Corrosion Resistance, Custom Sizes

Hot-dip galvanized rectangular tube is a versatile structural steel product designed for long-term use in harsh and diverse environments. Made from high-quality carbon steel or alloy steel, our galvanized rectangular hollow sections (RHS) undergo precision ERW welding and strict hot-dip galvanizing process, ensuring superior durability, corrosion resistance, and structural integrity. Unlike ordinary steel tubes, our product features a uniform, metallurgically bonded zinc coating that provides long-lasting protection against rust, moisture, and chemical erosion. Available in standard and custom sizes (outer dimensions: 15×30mm to 400×600mm, wall thickness: 1.0mm to 20mm), it is widely recognized for its easy installation, excellent load-bearing capacity, and cost-effectiveness, serving as a reliable material for construction, infrastructure, manufacturing, and more.

Many projects suffer from frequent maintenance, safety risks, and high replacement costs due to the limitations of traditional steel materials. Ordinary steel rectangular tubes, without effective anti-corrosion treatment, quickly rust and deteriorate when exposed to outdoor weather, humid interiors, industrial chemicals, or underground soil—leading to structural weakening and potential accidents. Additionally, inconsistent product quality in the market often results in tubes that fail to meet load-bearing requirements, causing project delays and additional expenses. For projects requiring long service life and low maintenance, traditional steel tubes cannot balance performance and cost, while inferior galvanized products with thin coatings or poor welding quality further exacerbate these problems.

Our hot-dip galvanized rectangular tube addresses these points with a comprehensive, high-quality solution. We use premium base materials (Q235A/B, Q345A/B, ASTM A500, EN 10219) and advanced ERW welding technology to ensure the tube’s structural strength and dimensional accuracy. The hot-dip galvanizing process—including strict pre-treatment (degreasing, pickling, fluxing) and precise temperature control—creates a thick, dense zinc coating (≥60μm) that forms a barrier between the steel substrate and corrosive elements. This coating not only prevents rust but also offers cathodic protection, extending the tube’s service life significantly. We also provide flexible customization options, including non-standard sizes, custom lengths, and on-demand processing (cutting, punching, threading), to fit unique project needs. Our products are fully tested and certified, ensuring consistent quality and compliance with international standards, reducing maintenance costs and project risks.

Steel Coil → Slitting → Forming → ERW Welding → Sizing → Cutting → Passivation → Packing

This continuous production ensures:

• Stable welding seam
• Accurate dimensions
• Consistent coating

The performance of galvanized rectangular tube relies on two core processes: precision tube forming and hot-dip galvanizing. Here’s a detailed breakdown of how it works to deliver superior durability and corrosion resistance:

1.Tube Forming Process: First, high-quality steel coils are uncoiled and cut into appropriate widths. The steel sheet is then cold-formed into a rectangular shape through a series of rollers, ensuring consistent dimensions and smooth surfaces. Next, the edges of the rectangular profile are welded using high-frequency ERW technology—this process uses electric resistance to melt the steel edges, creating a strong, seamless weld. After welding, the tube is sized, straightened, and cut to the required length, forming a solid, uniform blank tube.

2.Hot-Dip Galvanizing Process: The blank tube undergoes strict pre-treatment to remove impurities that could affect coating adhesion. This includes degreasing (to remove oil), pickling (to eliminate rust and oxide layers), water washing (to remove acid residues), fluxing (to prevent oxidation), and preheating (to ensure uniform zinc adhesion). The pre-treated tube is then immersed in molten zinc (temperature maintained at 450-460℃) for a specific period. During immersion, zinc reacts with the steel surface to form a dense zinc-iron alloy layer, followed by a pure zinc layer on top. After immersion, the tube is cooled, finished (to remove excess zinc), and inspected to ensure a uniform, defect-free coating.

3.Corrosion Protection Mechanism: The dual-layer zinc coating (alloy layer + pure zinc layer) acts as a protective barrier. The pure zinc layer prevents air, moisture, and corrosive media from contacting the steel substrate. If the coating is slightly damaged, zinc—with a higher electrode potential than steel—acts as an anode and corrodes first, protecting the steel (cathodic protection). This dual protection ensures long-term rust resistance and extends the tube’s service life.

• Packing (Bundles / Seaworthy Packaging)
• Tagging
• Weight Checking
• Trucking / Shipment