Ruspert Coated 304 Stainless Steel Bi-Metal Self Drilling Roofing Screws

Ruspert coated bi-metal self drilling roofing screws for the most corrosive metal roofing applications: a non-magnetic 304 austenitic stainless steel shank, friction-welded to a hardened alloy steel drill point, combines the corrosion resistance of stainless steel with the penetration power of hardened steel. The ceramic-based Ruspert coating is sintered at max 220°C into a tough 20μm barrier - well below the 450-900°C sensitization range - so the chromium passivation layer and the strength of the stainless steel remain fully intact; the coating is rated AS 3566 Class 4 and EU RoHS compliant. Three coordinated defenses stop galvanic (bi-metallic) corrosion after installation: a 300-series stainless washer with weather-resistant EPDM keeps water out so no electrolytic circuit can form; the ceramic barrier isolates the screw from dissimilar metals; and a 2μm zinc interlayer works as a sacrificial anode at the contact points between the screw and the fixed steel. Cold-forged with no heat treatment, the 304 shank retains the high ductility that resists fatigue fracture under wind-induced vibration. Available in diameters 4.8 / 5.5 / 6.3 mm, lengths 22-125 mm and drill points #1-#5 for steel 1.0-12.0 mm, with hex head, stainless washer and EPDM sealing washer. The corrosion-proof roofing screw for coastal, marine, industrial and heavily polluted environments, SGS tested.