3-D distribution characteristics of the micro-defects in the PEO coating on ZM6 mg-alloy during corrosion

The 3-D distributions of the micro-defects in the PEO coating on ZM6 Mg-alloy were investigated using X-ray tomography (XRT) and confocal laser scanning microscopy (CLSM) in conjunction with scanning electron microscopy (SEM). The results showed that micro-defects with different sizes and shapes existed in the pristine PEO coating. The sizes, shapes, and numbers of micro-defects of the PEO coating in 3.5 % NaCl solution changed greatly with immersion time under the synergistic effects between corrosion and the extension of corrosion products. Finally, the through-defects were formed by connecting the adjacent micro-defects and the substrate corroded.