Investigation On Corrosion Behavior Of Ultra-fine Grained Cu Processed By Equal Channel Angular Pressing

Ultra-fine grained(UFG) material is a new type of material with excellent physical properties and chemical properties to meet the needs of social development.Equal Channel Angular Pressing(ECAP) is considered one of the most promising industrial technologies in all preparation technologies of UFG material.In this paper,UFG T1(0.2-0.3μm) was made by ECAP(Φ=90°,Ψ=20°),and the corrosion behaviors of ultra-fine grained(UFG) Cu and annealed coarse-grained(CG) Cu were studied in differnet systems through E-t curve, potentiodynamic polarization curve,electrochemical impedance spectroscopy(EIS),X-ray energy dispersion spectrometer and scanning electron microscopy.The main research results were as follows:(1) Under room temperature,in 0.5mol/L NaC1 solution,UFG Cu exhibited lower corrosion current density in comparison with CG counterpart.It was that with the extension of immersion time,the corrosion surface of UFG Cu was very smooth and more uniform,but the localized corrosion of CG Cu was very serious,which indicated that UFG Cu had a better corrosion resistance than CG Cu.Immersion 64h later,the corrosion current density of UFG Cu and CG Cu decreased,and the protective effect of corrosion products enhanced.(2) In 0.5mol/L NaC1 solution,with increasing temperature,the surface film porosity of UFG Cu and CG Cu increased,which made C^1- so easily spread in the passive film that their corrosion rate increased and the protective character against corrosion reduced.When the temperature reached 90℃,CG Cu exhibited higher corrosion current density and passivation current,which showed that CG Cu was more likely to suffer corrosion than UFG Cu.(3) Under room temperature,with increasing concentration of C^1-,the corrosion potential of UFG Cu and CG Cu decreased,meantime their corrosion current density, passivation current density and blunt-dimensional current all increased,which indicated that copper was more likely to suffer damage and its protective character against corrosion reduced.In 1.5mol/L C^1- solution,UFG Cu and CG Cu had corrosion and passivation process,which indicated that UFG Cu and CG Cu had similar corrosion resistance.(4) Under room temperature,in 0.5mol/L NaC1 solution with S^2-,with increasing concentrations of S^2-,the corrosion potential of UFG Cu and CG Cu decreased,and their corrosion current density increased,which indicated that copper's passive film was more likely to suffer damage and its corrosion resisting property reduced.In NaC1 solution with 0.01mol/L S^2-,UFG Cu had lower corrosion current density,earlier occurred passivation and showed better corrosion resistance than CG Cu.(5) Under room temperature,in HC1 solution,the corrosion current density of UFG Cu was higher than in NaC1 solution and NaOH solution.In NaOH solution,with increasing electrode potential,anodic polarization entered transpassive region,the surface of UFG Cu dissoluted in a large current density,copper's passive film suffered damage on the local scale, and corrosion increased again.