Electrochemical Detection Of The Initial Corrosion Process Of Typical Metal Materials In Polluted Atmospheric Environment

Atmospheric corrosion is one of the most common corrosion forms of metal materials.The study on the corrosion initiation stage of metal materials by electrochemical method has a great significance to the study of corrosion mechanism,the life evaluation of metal components and the research and development of new materials.Electrochemical noise?EN?technology has great application prospect in atmospheric corrosion detection because of its simple equipment,on-line real-time detection and high sensitivity.In this paper,the electrode system and data processing method for EN detection of atmospheric corrosion are reviewed,and the early atmospheric corrosion process of typical metal materials is studied by combining EN with electrochemical impedance spectroscopy?EIS?.The feasibility of fuzzy Kolmogorov-Sinai?K-S?entropy in atmospheric corrosion of iron and steel materials was preliminarily explored.The electrochemical monitoring results of Q235B carbon steel show that EN can effectively monitor the corrosion process of carbon steel in atmospheric environment.In high humidity environment,the noise resistance R_n can well reflect the corrosion rate.In low humidity environment,the solution resistance has a certain effect on the monitoring results.The electrochemical detection results of T91 steel,LY12 and 7050 aluminum alloy show that EN can effectively monitor the initial and development of pitting.In high humidity environment,Cl^-can accelerate the rupture of passivation film,and the pitting initiation time is shorter.The results of EIS show that the low frequency impedance mode,charge transfer electron R_ct and noise resistance R_n are related to each other.The Bode diagram is basically consistent with the spectral noise resistance R_sn.The effect of surface orientation on pitting initiation was studied by electron back scatter diffraction?EBSD?.The results showed that the pitting of 7050 aluminum alloy and LY12 aluminum alloy first conceive and developed on the surface with higher surface energy.The fuzzy K-S entropy was used to study the corrosion images of Q235B carbon steel exposed to the marine atmosphere in Zhoushan.The results show that the K-S entropy increases with the corrosion increased.The relationship between fuzzy K-S entropy and corrosion weight loss is approximately linear mathematical expression.Fuzzy K-S entropy provides a new semiquantitative and rapid method for atmospheric corrosion detection.