Zinc-Tin Alloy Coated Self Drilling Roofing Screws for Metal Roofing

Zinc-tin alloy coated self drilling roofing screws engineered for fixing metal roof sheets, wall cladding and steel purlins. The dual-layer coating delivers Class 4 corrosion protection: a 45μm zinc-tin alloy base layer is mechanically plated 360° around the screw - covering even the irregular thread profile - so the zinc acts as a sacrificial anode and protects the carbon steel core; over it, a 15μm aluminum epoxy polymer topcoat is dip-applied and heat-cured, sealing the base layer and lubricating the screw during drilling, for a total thickness of ≥60μm. Corrosion performance: 1,500 hours salt spray resistance (ASTM B117 / GB/T 10125) and 25 Kesternich acid rain cycles (DIN 50018 / GB/T 9789), SGS verified and produced to AS 3566.2. The screw body is case-hardened C1022 carbon steel conforming to GB/T 3098.11 / ISO 10666; because the entire coating process runs at room temperature, with no acid pickling and no external electric field, the finished screws are free from hydrogen embrittlement and retain full strength. Available in diameters 4.8-7.0 mm, lengths 16-220 mm and drill points #1-#5 for steel 1.0-12.0 mm thick, with hex flange head and EPDM sealing washer. The metal roofing screw of choice for industrial, coastal and high-corrosion environments where ordinary zinc-plated roofing screws fail prematurely.