Electrochemical corrosion behaviour of Incoloy 800 in sulphate solutions containing hydrogen peroxide Tirdad Nickchi ⇑ , Akram Alfantazi Department of Materials Engineering, The University of British Columbia, Vancouver, BC, Canada V6T1Z4 article info Article history: Received 13 July 2010 Accepted 11 August 2010 Available online 17 August 2010 Keywords: A. Superalloys B. Polarization B. EIS C. Kinetic parameters abstract The aim of this study is to evaluate the electrochemical corrosion behaviour of Incoloy 800 in sulphate solutions containing H 2 O 2 in the temperature range of 25–80 °C. The open circuit potential measure- ments, cathodic and anodic polarization and electrochemical impedance spectroscopy (EIS) were used to characterize the corrosion behaviour. The results provide kinetic data for reduction of hydrogen per- oxide on Pt surface. The anodic polarization curves for Incoloy at different pH, temperature and H 2 O 2 con- centration are presented. EIS data generally confirm the polarization interpretations about the effects of various parameters. An equivalent circuit was used to fit all the acquired data. Ó 2010 Elsevier Ltd. All rights reserved. Introduction One of the promising designs for the Gen IV reactors is the supercritical water reactor, which benefits from high heat capacity of water in the supercritical state. Evaluation of corrosion issues for candidate materials for this reactor is important because the corro- sion mechanisms in supercritical water are not completely under- stood. Furthermore, the variation of water chemistry induced by gamma irradiation can affect the corrosion mechanisms. The irra- diation leads to generation of radicals in water [1] whose effects on corrosion should be evaluated. One of the most important of these species is hydrogen peroxide. In this regard, Glass et al. have reported that gamma irradiation leads to electrochemical potential shift, which is due to hydrogen peroxide generation [2]. Therefore, evaluation of effect of hydrogen peroxide on corrosion behaviour of active–passive alloys (due to their superior corrosion resistance) is essential. A literature survey shows that previous studies in this regard have evaluated the corrosion behaviour of alloys of interest in pressurized water reactors (PWR), constructional materials for tri- tiated water plants, and so on. These include evaluation of inter- granular stress corrosion cracking [3], and the crack growth rate [4] of 304 stainless steel in the presence of hydrogen peroxide, a comprehensive evaluation of welded S32550 duplex steel [5] and Inconel 690 [6] corrosion mechanism by Bellanger et al., and eval- uation of transpassivity of 304 stainless steel in hydrogen peroxide containing alkaline solutions [7]. In addition, recently, fundamen- tal studies regarding the interaction of H 2 O 2 with carbon steel sur- face and iron corrosion products have been carried out [8–10]. The high-temperature high-pressure evaluation of corrosion in the presence of H 2 O 2 has also been studied. These include the effect of water chemistry, including H 2 O 2 concentration, on elec- trochemical potential and corrosion rate of 304 stainless steel [11,12] and alloy 182 [12], and evaluation of electrochemical potential [13], polarization behaviour [14] and oxide film charac- terization [15,16] of stainless steels in the presence of H 2 O 2 . One of the possible candidate alloys to be used in Gen IV reac- tors is Incoloy 800 [17], due to its high temperature corrosion resistance. Some studies have evaluated its corrosion behaviour in high temperature aqueous solutions in terms of long-term immersion [18] and electrochemical studies [19], as well as the oxidation behaviour in supercritical water simulated environments [20]. The aim of our research is to evaluate the corrosion behaviour of Incoloy 800 in the presence of hydrogen peroxide, due to its sig- nificance in establishing the corrosion mechanism. As a first step, it is necessary to have a fundamental understanding of the effect of hydrogen peroxide on corrosion. Therefore, in this paper, we pres- ent the low temperature results as they provide a base line and a fundamental understanding of corrosion in this medium. 2. Experimental 2.1. Electrochemical methods A Princeton Applied Research (PAR) Versastat 4 potentiostat/ galvanostat was used for all the electrochemical measurements. The open circuit potential (OCP) measurements were carried out 0010-938X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2010.08.022 ⇑ Corresponding author. Tel.: +1 6047797544; fax: +1 6048223619. E-mail address: tirdadn@interchange.ubc.ca (T. Nickchi). Corrosion Science 52 (2010) 4035–4045 Contents lists available at ScienceDirect Corrosion Science journal homepage: www.elsevier.com/locate/corsci