Research And Development Of Blacking Agent For Low Temperature Steel Surface With Residual Heat

The low-temperature residual heat steel surface blacking agents is the process of using the heat of the workpiece itself at the time of low temperature tempering to deposit the blacking agent on the surface of the workpiece to form a dense black film.The appearance of the blacking film could be improved,the workpiece isolated and the environment corroded to form a closed film layer,so as to achieve the purpose of decorating the appearance and enhancing the service life of the workpiece.According to the references,water-based epoxy-resin acrylic resin is the main film-forming agent,and the appearance of the blacking film layer of other additives such as aqueous paste,corrosion inhibitor,coupling agent,leveling agent,and other film forming aids is studied by orthogonal test,which the morphology,corrosion resistance,adhesion is access to the basic formula.The details are as follows:1)Through the formulation primary selection,single factor,orthogonal optimization and comparative experiments,as the appearance,corrosion resistance and adhesion test results of the blacking film layer were taken as the testing standards.The formula for the low-temperature residual heat blacking agent,the content of each component in the formulation,and the blacking process are optimized.The identified blacking agent composition are as follows: aqueous epoxy acrylate resin GS-330,methyl etherified amino resin CYMEL 325,aqueous color paste SIP 3070,corrosion inhibitor CP-1000,coupling agent NXH-311 w,leveling agent Tego WET 270,bactericide BIT 20,defoamer Tego Foamex 810.The selected blacking agent process conditions are as follows: blacking solution pH 8.5,workpiece heating temperature 320℃,and workpiece holding time 55 minutes.2)The appearance,corrosion resistance,adhesion,film thickness,Tafel polarization curve,and SEM test were performed on the workpieces after the blacking process was optimized.According to the film appearance rating standard,the appearance of the blacking film layer could reach 95 on average.After the parallel neutral salt experiment,the salt film spray time of the blacking film layer could reach 237 minutes on average,and the salt spray resistance was close to 4 hours.The traditional blacking treatment has greatly improved and the adhesion of the blacking film could reach Class 1 and the average thickness of the film is13.6 μm.Through the Tafel polarization curve and SEM test results,it could be seen that after low temperature heat treatment blacking test A dense and uniform blacking film layer is formed on the surface of the sample,and this film layer significantly improves the salt spray resistance time of the metal substrate and plays a role in reducing metal corrosion.The innovation of this paper is to reduce the use temperature of residual heat blacking agent to between 250℃-350℃ to meet the requirements of blackened and anti-corrosion forsmall parts or special parts.The difficulty lies in the selection of suitable film-forming resins and other film-forming aids to further improve the appearance and corrosion resistance of the blacking film layer under the premise of ensuring that the low-temperature blacking agent can form films effectively.