Investigation of AZ91D Magnesium Alloy Corrosion Behavior under Thin Electrolyte Layer Using Nondestructive Electrochemical Techniques

摘要

In order to investigate the corrosion behavior of AZ91D magnesium alloy under thin electrolyte layers(TELs) in 3.5 wt. % NaCl solution during short immersion time, some nondestructive electrochemicalmeasurements such as the electrochemical impedance spectroscopy (EIS), electrochemical noise (EN)and cathodic polarization curves were conducted. In addition, scanning electron microscopy (SEM)attached with energy dispersive X-Ray spectroscopy (EDS) and Scanning Kelvin Probe ForceMicroscopy (SKPFM) were employed to character the microstructure and the Volta potentialdistribution of AZ91D magnesium alloy surface. The experimental results reveal that the corrosion rateof AZ91D under TELs is slower than that in bulk solution and decreases with the TEL thicknessthinning. Both the anodic and cathodic reactions were restrained under TELs, especially in thicknessthinning to around 200 m and lower. Furthermore, pitting corrosion is initiated at the matrix adjacentto the noble phase particles and crevice corrosion is dominant at the early corrosion stage under TEL.