External coating repair refers to the pipeline outside the coating caused by the construction of local damage and handling and other factors caused by the modification of the damage, including the pipe joints outside the construction of the coating and damage repair. The standard for repair shall not be less than the relevant standard of the technical specification. The external coating of the duplex stainless steel pipe shall be made intact, the stainless steel pipe is not allowed to be exposed or the coating is clearly thinned due to damage, or the coating is not tightly adherent. Once the steel pipe is exposed, it is necessary to carefully remove the rust and dirt from the exposed area, remove it with wire or other means, and repair it after being sure that it is clean and dry. Repair the first use of approved quick-drying paint backing, those embedded in the coating of small stones should be picked out, and then localized with a spray gun coating, with a repair knife to repair the coating flat, if necessary, add the outer coating. The use of anti-corrosion tape anti-corrosion parts of the repair should be stripped of the injury site, coated with primer, and the use of the same tape, repair the overlap width must be greater than 100 mm damaged parts.