Enhancing the Electrochemical Behavior of Pure Copper by Cyclic Potentiodynamic Passivation: A Comparison between Coarse
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A variety of methods including physical, mechanical, chemical, and electrochemical processes have been proposed to improve the surface characteristics of materials and specifically its corrosion resistance.[1,2] One of the electrochemical surface modification methods, which has been less frequently studied, is cyclic potentiodynamic passivation (CPP). This technique can be fast, cost-effective, and environmentally friendly for corrosion protection. The studies conducted by Shahryari et al.[3–5] have revealed that both general and pitting corrosion resistance of 316LVM can be effectively enhanced through the application of CPP method. Moreover, it was shown that the 316LVM surfaces, which were modified by CPP method, offered a higher preosteoblast cell attachment when compared with the unmodified surfaces. Vukovic[6] reported that CPP improved the passive layer stability of AISI 302 stainless steel in an alkaline medium. It is worth mentioning that the effect of grain size, which is an important factor in metallurgical considerations, were not considered in any
ARASH FATTAH-ALHOSSEINI, Assistant Professor, and OMID IMANTALAB, Ph.D. Student, are with the Department of Materials Engineering, Bu-Ali Sina University, Hamedan 6517838695, Iran. Contact e-mails: [email protected], a.fattah@ basu.ac.ir FARID REZA ATTARZADEH, Junior Engineer, is with the Corrosion Division, Research Institute of Petroleum Industry, Tehran 1485733111, Iran. Manuscript submitted March 23, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
of the very limited studies which have been performed on the suitability of CPP on the corrosion resistance of metals or alloys. Undoubtedly, grain refinement process is considered to be of a paramount importance in changing mechanical properties of metals and alloys.[7] Owing to its profound impact on strength and ductility, the interest of many researchers has been attracted to perform different severe plastic deformations (SPD) such as high pressure torsion (HPT), multiaxial forging (MAF), equal channel angular pressing (ECAP), and accumulative roll bonding (ARB) as a surface or bulk preparation processes to produce ultrafine-grained (UFG) or nano-grained (NG) materials. ARB is a suitable method in order to fabricate NG sheets and plates.[8,9] Although the positive effects of grain refinement on the mechanical properties of metals are well-defined, studies of its impact on electrochemical behavior are nevertheless few.[10,11] Despite the fact that some articles have been published concerning the corrosion and passive behavior of copper and its alloys,[12–17] there is still a serious lack of knowledge on the effect of grain refinement on the electrochemical behavior of copper and its alloys. Indeed, the microstructure, which is definitely influenced by the forming process, can affect the passive film formation and its behavior. Recently, Nikfahm et al.[18,19] evaluated the corrosion behavior of UFG copper produced by ARB process in 3.5 wt pct NaCl solutions at different pH values. Additionally, in our previous stud
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