(1) Pre-treatment removes contaminants, oxide scales, welding slag, and other impurities from the inner wall of the steel pipe. It also smooths the inner surface of the steel pipe and reduces internal surface stress. This effectively enhances the service life of the steel pipe, mitigates internal corrosion, and thereby improves both the internal and external quality of the steel pipe.
(2) Additionally, pre-treatment increases the friction force between the metal pipe and the plastic lining, thereby enhancing the bonding strength.
