Galvanized Square & Rectangular Tube

Galvanized square tube and galvanized rectangular tube is a metal tubing with a zinc layer applied to the surface of a square or rectangular steel tube (black tube) via a hot-dip or electroplating process. It combines the mechanical properties of steel tube with the corrosion resistance of zinc.

Galvanized Square and Rectangular TubeProduction Process:

Galvanized square and rectangular tube is categorized by the production process as hot-dip galvanized square and rectangular tubing and cold-dip galvanized square and rectangular tubing. The differences in the processing of these two types of galvanized square tubing result in distinct physical and chemical properties. Generally speaking, they differ significantly in strength, toughness, and mechanical properties.

Hot-dip galvanized square and rectangular tube:
Hot-dip galvanized ERW square and rectangular tubing is a square tubing made by rolling and welding steel sheets or strips. This tubing is then placed in a hot-dip galvanizing bath and undergoes a series of chemical reactions to form the tubing. The production process for hot-dip galvanized square and rectangular tubing is relatively simple, offering high production efficiency and a wide variety of specifications. This type of tubing requires minimal equipment and capital, making it suitable for small galvanized square tube manufacturers. However, the strength of this type of steel pipe is far lower than that of seamless square pipe. Industry standards: ASTM A123, EN ISO 1461 (European standard).

Cold-dip galvanized square and rectangular tube:
Cold-dip galvanized square pipe utilizes the cold-dip galvanizing process to impart corrosion resistance to the square pipe. Unlike hot-dip galvanizing, cold-dip galvanizing primarily utilizes an electrochemical mechanism for corrosion protection. Therefore, sufficient contact between the zinc powder and the steel must be ensured to generate an electrode potential difference, making steel surface treatment crucial. Industry standard: ASTM B633 (Class Fe/Zn 8).

Differences between hot-dip galvanizing and cold-dip galvanizing:
Galvanized square pipes are classified into two categories: hot-dip galvanized and electro-galvanized. Hot-dip galvanizing can be performed using wet, dry, lead-zinc, and redox methods. The primary difference between different hot-dip galvanizing methods lies in the method used to activate the pipe surface after acid cleaning to improve the quality of the galvanizing. The dry and redox methods are currently used in production; their characteristics are shown in the table. The electrogalvanized zinc coating is remarkably smooth, dense, and uniform in structure. It exhibits excellent mechanical properties and corrosion resistance, and its zinc consumption is 60% to 75% lower than hot-dip galvanizing. While technically complex, electrogalvanizing is essential for single-sided coating, double-sided coating with varying thicknesses on the inner and outer surfaces, and thin-walled pipe galvanizing.

Galvanized Square Tube Size Options:
Lightweight Structures: Choose sizes 40×40×2.0mm or smaller
Load-Bearing Structures: Choose sizes 80×80×4.0mm or larger
Harsh Environments: Zinc coating ≥80μm + Powder Coating for dual protection

Galvanized Rectangular Tube Size Options:
Lightweight Structures: Choose sizes 40×20×2.0mm or smaller (electrogalvanizing is more economical)
Load-Bearing Frames: Choose sizes 80×40×3.0mm or larger (hot-dip galvanizing provides greater durability)
Extreme Environments: Specify zinc-aluminum-magnesium coatings (such as ZM310)

Applications of Galvanized Square & Rectangular Tube:
Because galvanized square and rectangular tubes are galvanized, their applications are significantly expanded compared to square tubes. They are primarily used in curtain walls, construction, machinery manufacturing, steel construction projects, shipbuilding, solar panels, steel structures, power plants, agricultural and chemical machinery, glass curtain walls, automotive chassis, and airports.

Read more: ASTM A500 Square Tube or Square tube vs Rectangular tube