(1) Pretreatment can remove contaminants, oxide scales, welding slag, and other impurities from the inner wall of steel pipes. It also prepares the inner surface of the steel pipe and reduces internal surface stress. This effectively enhances the service life of the steel pipe, minimizes internal corrosion, and thus improves both the internal and external quality of the steel pipe.
(2) Additionally, pretreatment increases the friction force between the metal pipe and the plastic lining, thereby enhancing their bonding strength.
