Research On Low Phosphorus Passivation And Antirust Technology, Mechanism And Application Of Steel-based Molybdate

Iron and steel parts are easy to return to rust before painting after being washed by pickling and washing during processing.Steel parts need to be rust-proofed before painting.The most widely used process is the phosphating process,which is more polluting.This subject studies the corrosion protection technology of steel pipe fittings and develops a new molybdate-based,low-phosphorus new passivation process to replace phosphating,so that the surface of steel parts can be kept smooth and clean for a certain period of time after pickling,thus enhancing In the subsequent coating process,the binding force and corrosion resistance of the paint film reduce the pollution caused by phosphorus ions to the environment.Through a single factor experiment,the components and process conditions in the molybdate low phosphorus passivation solution were optimized,orthogonal experiments were designed,and the best formula and process conditions were selected: sodium molybdate 2.5 g/L,trisodium phosphate 1 g /L,boric acid 2 g/L,p H is about 6,passivation in 60 s,passivation at 30?,drying in a constant temperature drying oven at 200?.The surface of Q235 steel treated by this process can form a smooth and dense passivation film.The copper sulfate drip experiment,placement experiment and electrochemical experiment on the passivation film prove that the molybdate low phosphorus passivation process can greatly improve the corrosion resistance of the passivation film,and the corrosion resistance is higher than that in industrial applications.Steel samples treated with sodium nitrite.The film formation mechanism and corrosion resistance mechanism of the molybdate low phosphorus passivation process were analyzed,including the physical barrier effect of the passivation film and the electrochemical barrier effect of the passivation film.The composition and content of the surface elements and compounds of the passivation film were analyzed by XPS test.The main elements on the surface of the passivation film were oxygen,phosphorus and molybdenum.After narrow-scanning and peak-fitting the three elements of oxygen,phosphorus,and molybdenum on the surface,it is concluded that the passivation film is mainly composed of phosphate,molybdate,their crystalline hydrate,and molybdenum oxide.Through the open circuit potential test and drawing the open circuit potential-time curve,the growth behavior of the passivation film in the low molybdate passivation solution was characterized.The film formation process of the passivation film was analyzed.The growth process of the passivation film was divided into There are eight stages.Using SEM scanning electron microscope,it was found that the surface of the passivated Q235 steel substrate formed an irregular fine network structure.This process was applied in Shandong Weide Remanufacturing Co.,Ltd.,which improved the paint coating performance of the factory,and greatly improved the overall corrosion resistance of the radiator,which effectively improved the industrial production efficiency and avoided the massive rework.Economic losses and waste of resources.Therefore,the research of this subject has great industrial application value.