A steel structure new surface treatment and coating technology

1 Introduction
China s railway transportation several times greater speed, the railway locomotive vehicle design, production requirements are also getting higher and higher.The upgrading of products has become a pressing matter of the moment of the railway locomotive vehicle factory.Locomotive steel structure design increasingly used in high performance steel plate, the traditional steel structure surface treatment and coating technology has been unable to adapt to the requirements of production and development, the urgent need to find a meet design and technical requirements of the new surface treatment process.
2 surface treatment and coating technology of steel structure painting, in order to make the substrate and the coating has good adhesion, coating must be treated steel surface and the adjacent region of pretreatment.First of all, the surface must be clean, does not allow dust, oil, water or other dirt and loose oxide.Secondly, spraying, coating and substrate binding General mechanical combination, therefore, without affecting the coating quality under the premise, the coating and the substrate should be as much as possible to increase the contact area, the appropriate roughness is helpful to improve the adhesion of coating, coating service life extension.Related information: alkyd coatings used for manual surface rust coating, its service life is 2 ～ 3a, blasted to Sa2.5 level of service life for 10a.Pretreatment of steel surface directly affects the quality of coating engineering and apparent quality and the service life of the coating, and the surface treatment of the steel structure in cleanness and roughness directly affects the service life of coating.As much as possible to increase the contact area of the coating and the substrate, using mechanical roughening and sandblasting roughening method.Mechanical roughening includes shot peening, manual grinding and polishing processing.Sandblasting coarsening is the choice of diameter of 1 ~ 2mm dry and sharp sand and quartz sand, the sand from the use of compressed air blasting gun gun mouth high-speed jet to steel surface by sand, impact and friction, the steel surface oxide skin, rust, paint film, grease and other dirt removing, obtained at the same time having a certain roughness surface process.In general, the higher the grade of steel, surface treatment of the requirements of the higher.Sandblasted surfaces of steel structures, surface area is about not be sandblasted steel surface area 90 times, greatly increases the contact area between the substrate and the coating.This to some coatings, particularly inorganic zinc-rich coating coating adhesion effects greatly.
3 primary problems in the process of previously, locomotive and vehicle (including steel structure with steel plates and profiles) surface treatment method, one is just a simple scaling, the cold, heat processing, welding steel structure, the steel structure surface spraying primer.This process by a variety of models of the spot application, proof antiseptic effect.A second method is the surface of steel, after chemical treatment (usually phosphating treatment), directly after the primer spraying, and then welding steel structure.The drawback is often appear primer and phosphating film supporting not good question, resulting in reduced adhesion phenomena such as primer.Also, in recent years also uses a process, steel to be sandblasted, and then directly spraying anti-corrosion primer, also has the problem of poor, and even affect the next process.
4 new technology scheme according to the existing problems of the original process, to achieve process, design requirements, taking into account the process of inheritance and continuity, the theory as the basis, through the test, decided by sandblasting and precoating primer combination of surface treatment and coating process.