Title: Exfoliation corrosion of Mg-14Li-1Ca alloysexposed to marine atmosphere for one year

Abstract

Magnesium (Mg) and its alloys hold promising applications in automotive, 3Cproducts (computer, communication and consumer Electronic) and biomedical fields due to their low density, high damping capacity, good castability and recyclability as well as excellent biocompatibility. However, they are prone to corrosion in aggressive solutions. The low corrosion resistance of Mg alloys is a major concern for extensive utilization, especially for load-bearing structure materials. So far, exfoliation corrosion of magnesium alloys has scarcely been reported. The microstructure, compositions and constitutes of as-extruded Mg-14Li-1Ca alloy has been investigated using field-emission scanning electron microscopy (SEM), EDS, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometry (FTIR) together with X-ray diffractometer (XRD). Electrochemical impedance spectroscopy and polarization as well as hydrogen evolution tests are applied to reveal the corrosion mechanisms. Results show that’s evere exfoliation corrosion occurs on extruded Mg-14Li-1Ca alloys exposed to marine atmosphere in a sea island field for almost one year. The findings are due to the elongated microstructure, and delamination or peeling off of the lamellar structure caused by galvanic and wedge effects. Galvanic effect between Mg2Ca particles and their neighboring α-Mg matrix facilitates preferred dissolution of Mg2Ca particles prior to α-Mg matrix; wedge effect is caused by the formation of corrosion products and hydrogen evolution.