Hot-Dip Galvanized Steel Coils

ASTM A653 is the American standard designating mechanical properties by grades (e.g., CS Type B, SS Grade 33/50) with coating weights denoted as G30 to G90. EN 10346 is the European norm classifying forming and structural grades (e.g., DX51D, S350GD) with metric zinc designations like Z100 to Z275. JIS G3302 is the Japanese industrial standard specifying commercial SGCC and structural SGC400 grades.

Zinc coating weight directly determines atmospheric corrosion lifespan. A light Z60 (60 g/m² total both sides) coating provides short-term indoor protection or serves as a substrate for indoor prepainted panels. Heavy Z275 / G90 (275 g/m²) provides 20 to 50 years of maintenance-free service in typical rural, urban, and moderate industrial outdoor environments.

Spangle refers to the visible zinc crystal pattern formed during cooling. Regular spangle features prominent, decorative crystalline 'zinc flowers' created by controlled lead or antimony additives. Mini spangle has fine, barely visible crystals. Zero spangle (minimized) is rapidly quenched with zinc dust or chemical mist, producing an ultra-flat surface preferred for painting.

Zinc flaking occurs when the zinc-iron alloy layer is brittle or the bend radius is too sharp. Specifying lock-forming quality (LFQ/DX52D) with low-lead zinc baths and optimized roller clearances ensures the zinc layer deforms plastically alongside the base steel without peeling, cracking, or die fouling.

To prevent wet-storage white rust caused by moisture condensation in tightly wound coils during maritime shipping, coils undergo surface passivation: traditional hexavalent or eco-friendly trivalent chromating, organic anti-fingerprint (AFP) resin coating, or light vanishing oiling (500–1000 mg/m²).

Yes, master coils (typically 1000 mm, 1200 mm, 1219 mm, or 1250 mm wide weighing 5 to 10 tons) are precision-slit on high-speed rotary slitting lines into narrow baby coils (from 50 mm to 600 mm wide) with deburred edges tailored to specific purlin or guardrail profiles.

Buyers must specify steel grade and standard (e.g., EN 10346 S350GD+Z), base metal thickness and tolerance (e.g., 1.5 mm ±0.03 mm), coil width (mm), zinc coating mass (e.g., Z275), spangle appearance (zero/regular), surface treatment (passivated/oiled), inner coil diameter (508 mm or 610 mm), and maximum individual coil weight.