... carbon steel , stainless steel ,3.size:all size4.surface: zinc plated , plain ,black , H.D.G ,5.transportation: ... special materials. For finishing, we provide black oxide, zinc electroplating, phosphate, copper plating, mechanical galvanization, hot dip ... specifications or upon our customers' special requirements, in grades 4.8, 6.8, 8.8, 10.9, 12 ... are welcomed to visit us. spring washer zinc plated