| The problem of corrosion of metal materials is common in all sectors of the national economy?such as industry,agriculture,national defense,etc.?.Each year,scrap metal materials due to corrosion problems account for about one third of the total global metal production.This corrosion phenomenon not only increases the degree of pollution to the environment,but also causes catastrophic consequences.Therefore,accidents such as aircraft crashes,bridge collapses,boiler explosions,and oil and gas pipeline leaks due to corrosion are common.Therefore,from the purpose of using resources effectively and protecting the human living environment,it is urgent to study how to solve the problems caused by corrosion.The preparation of various composite coatings on the surface of parts is an effective method for the protection of metal materials.Electrochemical noise is one of the main contents of molecular dynamics.It refers to the non-equilibrium wave signal of the electrochemical state parameter in the metal during the evolution of the electrochemical dynamic system.This wave signal provides detailed information for the corrosion state of the metal.In this paper,Ni-TiN composite coating was prepared by ultrasonic electrodeposition on the surface of Q235 steel.The effects of different process parameters?concentration of nickel sulfate,Polar spacing between the two poles,type and content of surfactant,boric acid concentration and nickel chloride concentration?on microhardness and wear resistance of Ni-TiN composite coatings were systematically analyzed.Then,the parameters of different process conditions are optimized by uniform test.Using scanning electron microscope,energy spectrometer,atomic force microscope,X-ray diffractometer,nanometer indentation instrument and other instruments to test different Ni-TiN composite coating microstructure,composition,structure,interface binding force and other properties.It indicated that the Ni-TiN composite coating which was prepared by the process parameter P3(nickel sulfate concentration of 279.5 g·L-1,polar spacing of 3.3 cm,sodium dodecyl sulfate concentration of 159 mg·L-1,boric acid concentration of 30.7 g·L-1and nickel chloride concentration of 30.6 g·L-1)has smooth surface,tight structure,small grains,and good wear and erosion resistance.Finally,the corrosion of Ni-TiN composite coatings in simulated seawater is monitored by electrochemical noise technology,and the corrosion state of Ni-TiN composite coatings in different erosion stages is studied by means of noise analysis,time-domain analysis and frequency-domain analysis methods.The study found that at the beginning of soaking,the curves of potential noise and current noise are relatively smooth,and the electrochemical noise resistor 1/Rn value is small.Mainly due to uniform corrosion,that is the low corrosion rate of the composite coating at this time,making the surface of the composite coating The change is not obvious;In the middle of soaking,the curves of potential noise and current noise fluctuate greatly,and the electrical noise resistor1/Rn value rises abruptly.That increases the corrosion rate of the composite coating.At this time,the corrosion of the coating is more serious and its surface is rough.A large number of small holes appear,and the diameter of the small holes gradually increases;At the end of soaking,there are a large number of transient peaks in the curves of potential noise and current noise,and the electrochemical noise resistor 1/Rn value continues to increase.The corrosion rate of composite coatings is higher,and the size of corrosion holes on the coatings surface is further increased to become corrosion pits.At this time,the corrosion condition of the coatings surface is more serious.The mechanical properties of specimens with or without Ni-TiN nano-composite coatings under tensile conditions after corrosion in simulated seawater were tested respectively,so as to determine the effect of Ni-TiN nano-composite coatings on the mechanical properties of matrix under corrosion environment.The mechanical properties of specimens with or without Ni-TiN nano-composite coatings at different corrosion stages were tested,and the changes of mechanical properties of specimens with Ni-TiN coating at different corrosion stages were obtained. |
PDF Full Text Request