| 摘要 |
A steel fastener has an elongate shank, an enlarged head formed at one end of the shank, and a generally pointed tip formed at the other end of the shank. A grooved portion of the shank is formed with helical grooves defining helical ribs and with annular grooves defining annular rings. The shank has a cylindrical portion between the grooved portion and the tip and a cylindrical portion between the grooved portion and the head. Each of the annular grooves has a root where deepest and each of the annular rings has a crest where largest. The roots define an imaginary cone diverging toward the tip. The crests define an imaginary cone converging toward the tip. The shank has an exterior surface coated with a polymeric coating, which is formed from an aqueous composition containing a water-based acrylic resin and a water-based polyurethane resin. A zinc layer anda chromate conversion layer are provided between the polymeric coating and the exterior surface of the shank. |
