Micro-electrochemical Properties and Pitting Corrosion Resistance of Microstructures of Carbon Steels

This paper presents an introduction of the relationship between the electrochemical properties of microstructures and pitting corrosion resistance of carbon steels in chloride-containing near-neutral pH environments. Recent investigations by micro-scale electrochemical measurements have been demonstrated that the pitting corrosion resistance of typical microstructures was ordered as follows: (high) as-quenched martensite > primary ferrite > pearlite (low). In the case of pearlite, it has been reported that pits proceeded along the lamellar structure consisted of Fe3C and ferrite. On the other hand, in the case of martensite, according to the studies based on the first-principles calculations, it has been proposed that the superior corrosion resistance was related with the electronic interaction between Fe and interstitial C. It was reported that the electronic density of states of Fe around the Fermi level decreased by the presence of interstitial C.