Corrosion Behavior of Alloy 600 Coupled with Electrodeposited Magnetite in Simulated Secondary Water of PWRs

Corrosion Behavior of SA508 Coupled with and without Magnetite in EDTA-Based Solutions

“…As shown in Table 2, when equal areas of SA508 and magnetite are galvanically coupled, the corrosion rate of SA508 will increase by a factor of approximately 600, from 0.028 mA/cm 2 to 16.85 mA/cm 2 . Therefore, this result agrees with the previous results that a galvanic coupling increased the corrosion rate of the materials coupled to magnetite in various aqueous solutions [5,7,9,24]. On the other hand, the Tafel constants of SA508 estimated from the polarization curves were 0.1034 V for the anodic reaction and 0.0923 V for the cathodic reaction.…”

“…Various methods for the manufacture of magnetite electrodes have been reported in the literature: casting molten magnetite [15,16], sintering magnetite powder [17,18], sputtering deposition [19], etc. However, a simpler method was recently developed to electrodeposit a magnetite layer onto carbon steel and Ni-based alloy substrates [20][21][22][23], and was verified to be useful for making electrochemical electrodes [4][5][6][7][8][9].…”

“…It has been reported that a galvanic coupling with magnetite accelerates the corrosion of secondary system materials: carbon steel [4][5][6], alloy 600 [7] and alloy 690 [8,9] in various environments simulating the secondary conditions of SGs. Most of the tubes and heated crevices in operating SGs are covered with deposits or sludge.…”

Micro-Galvanic Corrosion of Steam Generator Materials within Pores of Magnetite Flakes in Alkaline Solutions

“…Recently, many investigations on the galvanic effect by magnetite on the corrosion behavior of secondary coolant system materials such as nickel-based alloys [4][5][6] and carbon steel [7][8][9] have been reported. It is well known that the SG deposits mainly consist of magnetite and are porous in nature [10,11].…”

“…Hence, an electric contact between SG structural materials and magnetite deposits could be occurred. In various secondary environments, it was reported that the corrosion potential of magnetite was higher than those of secondary system materials and the corrosion rate of the SG materials was greatly increased due to the shift in their potentials to the anodic direction [4][5][6][7][8][9]. Through the galvanic effect of magnetite on the SG materials, the mechanism on the galvanic corrosion of the secondary system materials coupled to magnetite is well established.…”