Metal pipes are usually treated with a paint coating that must be tightly bonded to the pipe surface for a long service life. Usually, the coating adheres to the surface of the metal pipe because of the sub-contracting attraction between the molecules. The size of the attraction is inversely proportional to the 6th power of the intermolecular distance, and the closer it is, the more attractive the range must be within 5A. , that is, within 3 times the diameter of the oxygen atom. Therefore, if there is oil on the surface, even if the oiliness of the monolayer will exceed 5A, the coating layer will lose its adhesion; and the free energy of the metal surface is very high, which may reach 4×10-3N/cm, and the surface free energy of the coating. The lower is about (2~6)×10-4N/cm; the expression of the adhesion work of the surface of the smooth metal pipe to the coating is: W=(γL-γM)+γN Where γL is the surface free energy of the solid; γM——the surface free energy of the interface; γN - the surface free energy of the coating; When γL > γN and the adhesion work is positive, the coating will automatically wet the surface of the metal pipe. However, when there is oil on the surface of the metal pipe, the free energy of the surface is reduced to 4×10-3N/cm, even better than some. The free energy of the coating is lower. At this time, not only the wetting adhesion is seriously reduced, but also the shrinkage cavities are caused, so that the coating cannot be firmly adhered to the surface of the metal pipe, so the degreasing treatment must be performed in the surface treatment of the metal pipe. Concerned about surprises Tag: metal pipe, monolayer, degreasing, free energy, metal surface Previous: An improved formulation of trivalent chromium color passivation solution Next: Pipeline application of sanitary standards in water supply pipeline engineering Side Discharge Lawn Mower, Automatic Lawn Mowers, Push Type Lawn Mower, Hand Push Lawn Mower Zhejiang Taizhou Wangye Power Co., Ltd , http://www.wyengine.com