Electrochemical Noise Characteristics of Corrosion Behavior of Al-based Hydrotalcite Coatings

The corrosion behavior of Al-based hydrotalcite coatings in 3.5% NaCl solution was characterized by electrochemical noise analysis technique. The corrosion process of electrodes was studied in detail by analyzing time-domain and frequency-domain characteristics of electrochemical noise (EN) together with morphology features. The results showed that the pitting corrosion process of coatings could be divided into four different stages. At passivated stage, the EN fluctuated slightly, and the parameters were relatively stable. At metastable pitting nucleation stage, the EN began to fluctuate obviously, σV, σI, W and fc increased, Rn decreased. At stable pitting corrosion stage, the potential declined rapidly and rised slowly, meanwhile various parameters tended to extremum and Li (localization index) was close to 1. At later pitting corrosion stage, the EN fluctuated slightly and various parameters tended to be weakened.