Black Phosphated Tube Description To protect the surface of NBK in a very good condition,we alsways use Black Phosphated. We have many experience in Black Phosphated and NBK tubes,as we said,we are just in exporting seamless steel tube,different kinds,different process, supply products and service better and better. KWK Steel Co.,Ltd Tel/Fax:+86-574-82050027 Email:culture007@gmail.com Address:Haishu District,Ningbo,China