Galvanic corrosion study between low alloy steel A508 and 309/308 L stainless steel dissimilar metals: A case study of the effects of oxide film and exposure time
By Okonkwo, Bright O.; Ming, Hongliang; Meng, Fanjiang; Wang, Jianqiu; Xu, Xuelian; Han, En-Hou
Published in Journal of Nuclear Materials
2021
Abstract
The effects of oxide film and exposure time on the galvanic corrosion between low alloy steel (LAS) A508 and 309/308L stainless steel (SS) dissimilar metals were studied by several electrochemical techniques and surface composition analytical tools. The zero resistance ammeter (ZRA) result shows that the trend of galvanic corrosion current between the coupled LAS A508 and 309/308L SS changes with respect to exposure time. Furthermore, from the ZRA measurement, the quantitative relationship between galvanic current and dissolution rate of the coupled LAS A508 anode metal was established by statistical approach. Electrochemical impedance spectroscopy (EIS) results and analyses demonstrated that the increasing galvanic corrosion rate observed between the coupled dissimilar metals as exposure time prolonged was suppressed by the oxide film effect. The suppression occurred as a result of the transformation of unstable oxides to stable oxide forms, and the oxide film thickening phenomenon experienced on the LAS A508 surface as exposure time prolonged. Generally, a synergy between both effects was observed in this study.