The Study Of Electrochemical Noise Technique On The Initial Corrosion Behavior Of Typical Metals

Copper and steel are commonly used industrial materials,however,they still suffer from serious damage during their long time serving processes,especially in highly aggressive environments.Therefore,this project is of great significance to study the mechanism of metal corrosion and the protection of corrosion inhibitor.Generally,the mainstream electrochemical methods to describe corrosion process of metal are electrochemical impedance spectroscopy(EIS)and polarization,however,they exert disturbances to the investigated systems,and cannot be used for in-situ corrosion determination.Electrochemical noise(EN)technique has been widely used in the corrosion research,but the quantitative information about the corrosion process from noise energy viewpoint has not been reported.The main technique used in this paper is electrochemical noise,and combined with EIS,SEM,XPS,and QCM et al.This paper systematically studied the initial corrosion behavior of typical metal,served in atmospheric environment,marine environment and industrical environment.And this paper also discussed the evolution of electrochemical noise energy and extended the application of electrochemical noise technology.The third chapter mainly explores the Energy Distribution Plot and the Power Spectral Density spectra changing with the increasing testing frequency until 8 Hz.The corrosion energy(Ec)of EN,deduced from Fast Wavelet Transform method,showed the similar variation trend of copper corrosion rate served in atmospheric,thin electrolyte layer,and bulk solution.Hence,the proposed parameter E,represented the corrosion rate or severity,and the corrosion degree of metal was effectively monitored by in-situ electrochemical noise technique.The fourth chapter mainly discussed copper corrosion in 70%RH environment at 25 0C with NaCl deposited.The oxygen and moisture will asorbed onto copper surface,and lead to significant atmospheric corrosion in such condition.Both corrosion severity and surface roughness of copper increase with corrosion time or CNaCl.The corrosion product of copper during its initial atmospheric corrosion process(? 1 h)is Cu2O,which is independent of Nacl(15?60 ?g·cm-2).The electrochemical active energy(Ec)is both directly proportional to the corrosion severity and[Cl-]2,and the rising rate of Ec with corrosion time at different NaCl concentration may be used to deduce the corrosion mechanism.The fifth chapter explores the inhibition effects of BTAH on copper unde thin electrolyte films.The corrosion inhibitor BTAH was chemisorption onto copper surface through Cu-N bond tightly,leading to[Cu(I)BTA]n film which has verified by theoretical calculation and EIS experimental characterization.Corrosion rate increases as TEL thickness decreases which controlled by diffusion-controlled process.The sixth chapter explores the inhibition effects of HPAA and KPP on Q235 steel in simulated formation water.HPAA and KPP are mainly chemically and physically adsorbed onto Q235 surface in simulated formation water at 60 ?,respectively.While blended together,the physical adsorption of KPP is somewhat faster than the chemisorption of HPAA,but HPAA begins to play a dominantly protective role after 15 min.The difference in the RP-EDP region,where the EN energy is mostly accumulated,may be adopted to distinguish the chemisorption and physical adsorption of inhibitors.At last,the variation tendency of Rct obtained by EIS technique is just opposite to that of Dfobtained by EN technique,which hint that the initial corrosion processes of metals can be in-situ monitored by using EN technique expediently.