Key points of steel structure surface treatment and coating process

Before the steel structure is painted, to ensure good bonding performance between the coating and the substrate, the surface of the steel to be painted and the nearby area must be pretreated. First of all, its surface must be clean, and no dust, oil, water stains, or other dirt and loose oxides are allowed. Secondly, when spraying, the combination of the coating and the substrate is generally mechanical. Therefore, without affecting the spraying quality, the contact area between the coating and the substrate should be increased as much as possible. Appropriate roughness helps to improve film adhesion and extends coating life. Relevant information: Alkyd coating is used for manual surface rust removal. The service life of the coating is 2 to 3 years. The service life of sandblasting up to Sa2.5 level can be 10 years. The quality of steel surface pretreatment directly affects the apparent quality of the coating project and the service life of the coating, while the cleanliness and roughness of the steel structure surface treatment directly affect the service life of the coating. To increase the contact area between the coating and the substrate as much as possible, mechanical roughening and sandblasting roughening methods are generally used. Mechanical roughening includes shot peening, manual grinding, and polishing. Sandblasting roughening is to use dry and angular yellow sand or quartz sand with a diameter of 1 to 2mm. Compressed air is used to spray the sand grains from the nozzle of the sandblasting gun to the steel surface at high speed. The impact and friction of the sand grains are used to roughen the steel surface. A process method that removes scale, rust, paint film, grease, and other dirt while obtaining a surface with a certain roughness. Generally speaking, the higher the grade of steel, the higher the surface treatment requirements. The surface area of the steel structure surface that has been sandblasted is approximately 90 times that of the steel without sandblasting treatment, which greatly increases the contact area between the coating and the substrate. This has a great impact on the adhesion of some paint films, especially inorganic zinc-rich paint films.