Abstract: Briefed here in the article are the characteristics of the hot dip galvanizing-epoxy powder duplex protective coating system for the steel pipe. Analyzed in detail is the effect on the adhesion of the powder coating by the water cooling and passivation,and the surface treatment of the galvanized layer after the hot-dip galvanizing of steel pipe. It is regarded via the analysis that the processes and operation procedures for the water cooling,passivation and surface treatment should be formulated according to the weathering state of galvanized layer. It is recommended to adopt a brush-off blast cleaning (or sweep blast-cleaning) to clean the surface of the zinc layer so as to obtain appropriate surface roughness contour to improve the adhesion of the powder coating.