Development of Electrochemical Surface Treatment for Improvement of Localized Corrosion Resistance of Zirconium in Chloride Environment

Abstract

An electrochemical surface treatment technique was developed in this study to improve the localized corrosion resistance of zirconium in a chloride ion environment. A combination of anodic and cathodic polarization cycles was applied to induce the selective dissolution of the inclusions that could potentially initiate the localized corrosion of zirconium. Shallow dips were observed on the specimen surface after the treatment, thereby indicating the dissolution of the inclusions. The electrochemical treatments via galvanostatic anodic polarization and potentiostatic cathodic polarization in concentrated phosphate-buffered saline resulted in a high pitting potential of greater than 2 V in a simulated body fluid. This indicated that the devised technique realized a significant increase in the localized corrosion resistance of the treated Zr.

Development of Electrochemical Surface Treatment to Visualize Critical Corrosion-Inducing Inclusions of Zr in Chloride Environments

“…Surface treatment.-As described in the introduction, an electrochemical surface treatment has been developed for improving the corrosion resistance of Zr by removing the critical inclusions that induce localized corrosion. 27 The treatment involves repeated anodic and cathodic polarizations under constant-current and constantpotential conditions, respectively. On applying anodic polarization at a constant current, the inclusions were forced to dissolve.…”

“…By this method, the inclusions that are exposed to the Zr surface, which are potentially the most susceptible to inducing pitting corrosion, are preferentially and spontaneously removed. 27 After the treatment, the surface of the Zr specimen exhibited many shallow pits that were traces of the dissolved inclusions. In addition, the pit size was reduced by decreasing the duration of anodic polarization 27 ; however, by doing so, the corrosion resistance did not improve as the inclusions remained in the pit due to insufficient dissolution.…”

“…27 After the treatment, the surface of the Zr specimen exhibited many shallow pits that were traces of the dissolved inclusions. In addition, the pit size was reduced by decreasing the duration of anodic polarization 27 ; however, by doing so, the corrosion resistance did not improve as the inclusions remained in the pit due to insufficient dissolution. In other words, the undissolved inclusions, which are the most corrosioninducing, were observed.…”

“…In our previous study, an electrochemical surface treatment was developed that enhances the corrosion resistance of Zr by removing the critical inclusions that induce localized corrosion. 27 The treatment involved repeated anodic and cathodic polarizations, after which the inclusions were dissolved. Furthermore, the inclusions that were potentially the most susceptible to inducing pitting corrosion were preferentially and spontaneously removed.…”

Best Papers Awarded in 2022 by <i>Materials Transactions</i>

“…In association with the awarded papers introduced above, popular topics that Materials Transactions published in recent years are grain boundary segregation 93) as Ito et al were concerned with, 4,30,49) creep deformation in a wide range of materials 94102) including tricrystals by Okada et al 103,104) and work hardening in various forms of deformation in an aluminum single crystal, 105) an A3104 aluminum alloy, 106) a Ti6Al4V alloy 107) and high-strength steels. 108) Furthermore, pitting corrosion resistance is also a popular issue reported by many research groups in terms of corrosion behavior of pure aluminum, 109) pure zirconium 110) and stainless steels. 111113) Readers who are interested in such topics may be worth checking them.…”