Electrochemical measurements of the corrosion of pure Fe and JLF-1 steel in HF-containing molten FLiNaK salt

• Published in: Fusion engineering and design 2021-01, Vol.162, p.112134, Article 112134
• Main Authors: Yamazaki, Gaku, Nagasaka, Takuya, Yagi, Juro, Goto, Takuya, Tanaka, Teruya, Watanabe, Takashi, Sagara, Akio
• Format: Article
• Language: English
• Subjects: Corrosion; Corrosion currents; Corrosion mechanisms; Corrosion rate; Current density; Electrochemical cells; Electrochemistry; Hydrogen fluoride; Iron; JLF-1 steel; Liquid blanket; Lithium fluoride; Molten FLiNaK salt; Partial pressure; Uniform attack (corrosion)
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2020.112134

•Pure Fe and JLF-1 steel corroded in molten FLiNaK salt with HF gas bubbling.•The corrosion current of pure Fe increased with the partial pressure of HF gas.•HF or H+ diffusion in FLiNaK was the rate-limiting corrosion process of pure Fe.•The corrosion rates of pure Fe and JLF-1 steel were close.•The presence of HF enhanced the boundary corrosion of pure Fe and JLF-1 steel. In order to establish a liquid blanket using a Li-containing molten fluoride salt, the corrosion rate and mechanism of pure Fe and JLF-1 steel in FLiNaK (LiF-NaF- KF = 46.5-11.5-42.0) was investigated by one of the electrochemical methods, the potential step method. Simulating the TF breeding in the blanket, HF gas was injected into FLiNaK at 773 K. The partial pressure of HF gas (pHF) was varied from 8.59 to 2.46 × 103 Pa. The current-potential curves of pure Fe and JLF-1 steel were measured in an electrochemical cell and fit by the Butler-Volmer equation with limited current density. The corrosion current density (icor) of pure Fe increased with pHF as icor=0.6pHF. The corrosion rates of pure Fe and JLF-1 steel were close. In order to keep the uniform corrosion rate of JLF-1 steel below 0.1 mm/year in the blanket, HF concentration in FLiNaK is required less than 1.2 × 10−4 molHF/m3. The cathodic current density (iLc) was proportional to pHF as iLc=-0.11pHF, and, therefore, the rate-limiting process of HF corrosion of pure Fe is predicted to be HF or H+ diffusion in FLiNaK.