Synopsis of process routing: cold drawn and bright NBK seamless steel tube is used as the tube to be phosphated, the phosphated is realized with the imported chemical fluid to form a black film, the antirust oil is absorbed by means of the micropore on the film to revent form the rust. the caps are covered at two ends of tube to prevent from the dust.

Main features: color of steel tube: bright black, color is homogeneously distributed on the tube sureface. the tube has good preperty of antirust.

Main application: used in hydraulic system, nested card connector (pipe joints) with matching.