Research On The Corrosion Behavior Of The Amorphous Coatings Applied In The Coupling Action Of Applied Loads And Corrosion Environments

Amorphous coatings are provided with enhanced mechanical properties and superior corrosion resistance,which can be suitable for the wide application of corrosive and abrasive field.The key factors that affect the failure of coatings are applied load and corrosion,however,there is still a lack of systematic research on the behavior with the coupling action of applied load and corrosion.Therefore,this systematic research can provide basis and references for the amorphous coatings applied in the coupling action of applied load and corrosion environments.Taking the amorphous coating as object of the research,the corrosion behavior of amorphous coating applied in the coupling action of applied load and corrosion environments are studied and the characteristics of normal passivation and corrosion behavior of amorphous coating by using electrochemical method are revealed in this thesis.Constant load and slow tensile tests are based to state the relationship between applied load and the passivation stability of the amorphous coating and establish influence of loads on the sensitive fracture behavior of amorphous coating,as well as putting forward the mechanism applied in the coupling action of applied load and corrosion environments,which provides a scientific basis for the application of amorphous coating applied in mechanics and corrosion.The main corrosion mode of the amorphous coating is uniform corrosion.The overall structure of the surface passivation film is stable and the local corrosion resistance is high.Under normal condition,the catalytic ability of acidification is enhanced with the increase of H+ concentration.The passivation current density increases,the passivation stability of the coating decreases and the pitting resistance remains unchanged with the increase of Clconcentration.Under constant load and slow tension tests,the passivation current rises and the passivation stability reduces with the increase of load,the concentration of H+ and Cl-.Besides,the p H value promotes the load corrosion of the amorphous coating.The uniform corrosion resistance and passivation stability of the coating reduces with the increase of temperature and loading time,which has effect on the corrosion.Under constant load,amorphous coating crack propagation expands around the main crack and forms the second cracks instead of linear brittle fracture.The anodic potential will promote anodic dissolution process and the environmental sensitive fracture,which is a typical anodic dissolution mechanism.Under slow tension tests,the second cracks are not formed and there is no obvious bifurcation in the process of crack propagation.Local corrosion is preferentially localized at the surface defects and passive film defects.The load increases the sensitivity of local corrosion and promotes crack initiation and propagation through accelerating the diffusion of Cl-.Cracks propagate rapidly through the uniformly melted particles,which results in surface fracture.The coupling action of applied load and corrosion environments aggravates the environmental sensitive fracture process and has a definite risk of environmental sensitive fracture.