Zinc-Aluminum-Magnesium Coated Square Steel Tube

The main difference is the coating system rather than the square tube shape itself. Zinc provides the primary barrier protection, while aluminum and magnesium help improve the corrosion behavior of the coating. Around small areas of coating damage, the corrosion products can spread over the exposed steel and slow further corrosion.

This makes Zinc-Aluminum-Magnesium Coated Square Steel Tube particularly useful for outdoor fabrication, where cutting, drilling and other processing are common.

Available Sizes

Special sizes, wall thicknesses and lengths can be discussed according to drawings and project requirements.

Coating and Base Steel

The Zinc-Aluminum-Magnesium Coated Square Steel Tube is available in structural steel grades such as S350GD, S420GD and S550GD, with the selected grade depending on the load requirements of the finished structure.

For outdoor projects, the coating specification should also be confirmed separately. Coating performance depends on coating mass, substrate, forming process, processing after coating and the actual environment in which the tube will be installed.

Where It Fits Best

Solar Mounting Systems

Suitable for ground-mounted solar structures, rooftop PV supports and other outdoor photovoltaic components where corrosion resistance is an important consideration.

Outdoor Structural Work

Used for fences, guardrails, walkways, advertising frames, landscape structures and façade support frames.

Construction and Infrastructure

Applicable to factory auxiliary structures, greenhouse frames, equipment platforms and outdoor support members where the selected section meets the design load.

Equipment Manufacturing

Used for automation equipment frames, machinery structures, storage racks and logistics equipment.

Humid and Coastal Projects

Can be specified for humid or coastal environments when the coating level and corrosion protection system are matched to the exposure conditions.

Processing After Delivery

The Zinc-Aluminum-Magnesium Coated Square Steel Tube can be supplied with a range of fabrication operations, including fixed-length cutting, drilling, chamfering, beveling and other machining.

Welding is also possible, but the coating around the weld area will be affected by heat. For projects requiring welded joints, the post-weld treatment should be confirmed in advance so that the exposed steel receives suitable corrosion protection.

For large-volume structural projects, pre-cutting and drilling can also reduce site fabrication work and improve installation efficiency.

How It Is Manufactured

Production generally starts with Zn-Al-Mg coated steel strip, which is formed into a square section and joined by high-frequency welding. The tube then passes through sizing, straightening, cutting and final inspection.

The important controls are not limited to the coating itself. Strip thickness, section dimensions, corner geometry, weld quality, straightness and coating condition all need to remain within the agreed specification.

Zn-Al-Mg Compared with Other Square Tubes

Actual corrosion resistance and service life depend on the coating specification and environmental exposure. Claims such as a fixed 25–30 year life or a specific salt-spray-hour rating should be based on an agreed test method and project condition rather than used as a universal value.

Inspection Points

Quality inspection can include:

Additional corrosion or salt-spray testing can be arranged when required by the customer's specification.

Cutting, Welding and Corrosion Protection

A key advantage of Zn-Al-Mg coated steel is its corrosion behavior around small areas of coating damage. However, this does not mean every cut or weld can be left untreated under all conditions.

For normal cutting and drilling, the extent of coating damage should be considered. For larger exposed areas or welded joints, a suitable touch-up or repair system may still be required, especially in severe coastal or industrial environments.

Ordering Guide

For quotation, provide the following basic information:

Section size: for example 50 × 50 mm

Wall thickness: for example 2.0 mm

Steel grade: S350GD+ZM / S420GD+ZM / S550GD+ZM

Length: 6 m or custom length

Quantity: pieces or total weight

Application: PV, structure, equipment or other use

Processing: cutting, drilling, galvanizing or other requirements

For solar mounting and structural projects, drawings or loading requirements are helpful for confirming the appropriate section and grade.

FAQ

Q1: Is Zinc-Aluminum-Magnesium Coated Square Steel Tube the same as galvanized square tube?

No. Both are steel tubes with protective coatings, but the coating composition is different. Zn-Al-Mg uses a zinc-based alloy containing aluminum and magnesium, giving it different corrosion behavior from a conventional zinc coating.

Q2: Does Zn-Al-Mg coating protect a cut edge automatically?

It has a self-protecting effect around localized coating damage, which can slow corrosion from a small exposed area. It should not be understood as complete automatic repair. Large damaged areas and welded sections may still require additional protection.

Q3: Can Zn-Al-Mg square tube be welded?

Yes. It can be welded, but welding damages the coating locally because of heat. The required weld-area corrosion treatment should therefore be included in the project specification.

Q4: Is it suitable for photovoltaic structures?

Yes. Zn-Al-Mg coated square tube is commonly considered for outdoor PV structures because it combines a formed structural section with corrosion protection suitable for many outdoor environments.

Q5: What sizes are available?

The standard range provided here is 20 × 20 mm to 200 × 200 mm, with wall thicknesses from 1.2 to 10 mm and common 6 m lengths. Custom dimensions and lengths can be discussed for project orders.

Q6: Is it suitable for coastal areas?

It can be used in coastal environments, but the required coating level should be selected according to salt exposure, humidity, temperature and the required service life. Severe marine conditions may require additional protection beyond the base coating.

Q7: What is the advantage over black steel tube with paint?

Zn-Al-Mg coating provides corrosion protection directly on the steel surface and is not dependent on a conventional paint film alone. This can reduce maintenance requirements in suitable outdoor applications, while the final result still depends on the coating specification and environment.