Galvanized and Galvalume Steel Coil Z120 to Z275 for Middle East and African Roofing Projects

A roofing project in Jeddah, Dubai or Lagos lives or dies on two numbers that are printed in small text on the coil tag: coating weight and grade. Buyers who treat galvanized coil as a single commodity usually discover the difference eighteen months after the roof is installed, when the first red rust appears at the cut edges of a coastal warehouse.

Coating weight is the specification, not a detail

Z120, Z180, Z275 and AZ150 are not marketing labels. They describe how many grams of zinc (or zinc-aluminium) per square metre sit on the steel, and that number decides how long the sheet survives in a given environment.

In Gulf conditions the two failure modes are opposite and both expensive: salt-laden air attacks cut edges and lap joints, while intense day-night thermal cycling works on the paint system and on the fixings. In West and East Africa, the dominant issue is transport and storage humidity rather than atmospheric aggressiveness, which is why packing and inland handling matter as much as the coating class.

What to fix in the purchase order

• Standard and grade: DX51D+Z for bending and profiling, S250GD or S350GD for structural work, G550 full hard for purlins and decking.
• Spangle: regular spangle, minimized spangle or skin-passed. Skin-passed material takes paint and adhesive better; regular spangle is the traditional roofing look.
• Dimensions: thickness 0.15 mm to 3.0 mm, width 600 mm to 1500 mm, coil ID 508 mm or 610 mm, coil weight agreed to suit the customer's roll former.
• Surface treatment: chromate passivation, anti-finger print, or oiled, depending on whether the coil will be stored for months before forming.
• Cut edge protection: if the sheet will be cut and left exposed, the coating class must be chosen for the cut edge, not only for the flat surface.

Documentation and inspections that matter

For each galvanized order we issue a mill test certificate that states the coating mass per square metre alongside the base metal chemistry and mechanical properties, because a certificate that only says "galvanized" cannot be checked at the port. Buyers who need independent verification can request third-party inspection by SGS or BV before loading, and we photograph the coil tags, the strapping and the container stowage so the buyer sees the coil that will actually arrive.

Shandong Dingcheng Liye Materials Co., Ltd has been supplying steel from the Shandong mill base since 2011, operating as manufacturer, importer, exporter and trading company with 20 to 50 employees and an export share of about 50 to 60 percent. Galvanized and galvalume coil sits in the same warehouse system as hot rolled plate, cold rolled sheet, pipe and rebar, which allows a roofing contractor to consolidate coil for the roof, pipe for the structure and rebar for the foundation in one shipment instead of four.

Practical advice before ordering

Send the destination city, not only the destination port. A coil for a coastal project and a coil for an inland project can look identical on the invoice while performing very differently after installation. State the expected service life, whether the material will be stored outdoors before forming, and whether the finished roof will be painted. With those three answers, the coating class and the surface treatment can be fixed in one exchange, and the shipment stops being a gamble on the weather.