Law, Mechanism And Application Of Electrochemical Noise In Common Metal

Electrochemical noise is the waves of potential and current with time in electrochemical corrosion process of the metal.The waves are generated by the reaction of electrochemical corrosion process itself,not with the interference of external disturbance,and it is closely related to the change of the metal surface and local environment.Therefore electrochemical noise can be used as a effective method to measure the metal corrosion,lots of in-situ and real information can be obtained concerning the metal corrosion process.In the foundation of referring to a great deal of literature,the paper summarize the development,the research status and background of electrochemical noise;firstly,discuss the factors influencing grinding and polishing in the progress of AZ91D magnesium alloy sample's production with SEM;secondly,research the electrochemical noise behavior of AZ91D magnesium alloy and its correspondence to the state of the surface of magnesium alloy in sodium chloride solution using electrochemical workstation,combining spectrum analysis,as well as the time-domain spectral and frequency-domain had been used to analyze and prove;and than using electrochemical noise synthetic system to study the electrochemical noise behavior of 20#pipeline steel in simulated produced water in oil and gas fields,some influence factors such as dissolved oxygen concentration,H2S partial pressure,Cl-,pH,salinity of water and temperature were studied;finally,we summarize the paper.Through experimental exploration,we reached the following important conclusions:(1)In grinding and polishing process of AZ91D magnesium alloy specimen,using SiC paper as abrasive,and all of water,alcohol and sodium hydroxide solution as grinding mediums can made SiC abrasive embed in magnesium alloy surface.Compared with water and alcohol,magnesium alloy grinding and polishing effect is the best which is using sodium hydroxide solution as grinding medium,and light grinding force is better than heavy grinding force.(2)There exist three process of corrosion for AZ91D magnesium alloy:the current and potential noise curves were no significant fluctuations in passive film forming stage;a sharp rise in current and sharp decline in potential with a small fluctuation in passive film breaking stage;current and potential noise curves synchronous anisotropy fluctuations passive film breaking and repairing stage.(3)There is the closely relationship between the pitting tendency of 20#steel in simulated produced water in oil and gas field and these affecting factors:dissolved oxygen concentration,H2S partial pressure,Cl-,pH,salinity of water and temperature.The pitting tendency of 20#steel is increased with the increasing dissolved oxygen concentrations,Cl'concentrations,salinity of water and temperature.And the pitting tendency of 20#steel is increased with the decreasing H2S partial pressure and pH.The electrochemical noise signals are different form inhibitors.The results were provided a solid theory foundation for electrochemical noise in-situ monitor/detection metal corrosion.