Standard External coating Refer to:NF A49-710、DIN30670、CAN CSA21、CAN CSA 20、SY/T0413、SY/T0315 and other country’s external anti-corrosion standards; Internal coating Refer to:NF A49-709、API RP 5L2、SY/T0457 and other other country’s external anti-corrosion standards;