Role of Cl− and NO3- ions on the corrosion behavior of 20% SiCp reinforced 6061-Al metal matrix composite: A correlation between electrochemical studies and atomic force microscopy

Effect of Cl− and NO3- ions on the corrosion behavior of 20% SiCp reinforced 6061-Al metal matrix composite has been studied using techniques like immersion, potentiostatic polarization, electrochemical impedance spectroscopy and scanning electron microscopy. The present investigation also identifies atomic force microscopy as one of the informative tools to reveal the extent of corrosion with a semi-quantitative approach. The corrosion parameters derived from different techniques revealed that the accelerated corrosion by Cl− is considerably suppressed in presence of NO3- in the medium. The NO3- ions can afford corrosion resistance to the matrix even in aerated conditions by autocatalytic conversion to nitrite and thereby suppresses the accompanying oxygen reduction reaction.