Combined Effect of Stress and Dissolved Oxygen on Corrosion Behavior of Ni-Cr-Mo-V High Strength Steel
In fact,Ni-Cr-Mo-V high strength steel is widely used as engineering structure material of ships-and equipment-building for the exploration of polar resources.However,high strength steel will suf-fer from corrosion in low temperature seawater environment.In case when the structure component of Ni-Cr-Mo-V high strength steel is subjected simultaneously to stress and corrosive seawater in this polar low temperature environment,its corrosion failure probability will be greatly aggravated.Therefore,it is of significance to clarify the service performance of Ni-Cr-Mo-V high strength steel in this environment.As thus,the corrosion behavior evolution of the steel in simulated low temperature seawaters with variation of dissolved oxygen contents was assessed in lab,while a four-point bending device was adopted as a means of applying stress on the testing steel.Results show that while a stress was applied on the test steel through banding in low temperature seawater,the increase of dissolved oxygen content will acceler-ate the formation of corrosion products on Ni-Cr-Mo-V high strength steel;correspondingly,Cr and Ni in the corrosion product layer decrease,which reduces the protective effect of the corrosion products layer on the substrate;when the dissolved oxygen content and the applied stress increase simultaneously,the Ni-Cr-Mo-V high strength steel will be further pseudo-passivated,resulting in an increase in its free-cor-rosion current density.It follows that in low temperature seawater environment,the applied stress and dis-solved oxygen have a synergistic effect on the corrosion of Ni-Cr-Mo-V high strength steel,which pro-motes the corrosion reaction of Ni-Cr-Mo-V high strength steel,resulting in the aggravation of surface corrosion and the decrease of the protective effect of corrosion products on the steel substrate.
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