The corrosion kinetics of duplex stainless steels DS2205 and DS2507 in molten carbonate salt at \(T = 500\,^{\circ }\textrm{C}\) and \(T = 600\,^{\circ }\textrm{C}\) are examined using a time-dependent power-law (TDPW) formulation that explicitly incorporates two characteristic time constants to distinguish early-stage and long-term corrosion behavior. Previously reported oxide scale thickness data are reanalyzed to assess the limitations of conventional power-law approaches based on time-independent growth exponents. The analysis shows that the asymptotic exponent \(\nu _0\) , which characterizes long-term corrosion kinetics, lies in the range \(1.07 \le \nu _0 \le 1.17\) for DS2205 and \(0.34 \le \nu _0 \le 0.37\) for DS2507 at \(T = 500\,^{\circ }\textrm{C}\) . At \(T = 600\,^{\circ }\textrm{C}\) , values of \(\nu _0 = 1.30\) and \(\nu _0 = 1.10\) are obtained for DS2205 and DS2507, respectively. Within the TDPW framework, \(\nu _0 = 0.5\) represents the criterion for diffusion-controlled growth of a passive oxide scale. On this basis, the corrosion behavior of DS2507 at \(T = 500\,^{\circ }\textrm{C}\) is consistent with diffusion-controlled growth of a protective oxide layer, whereas the remaining conditions exhibit sustained active contributions to oxide growth . These findings are consistent with reported microstructural observations, including oxide scale non-uniformity and phase separation at elevated temperatures. The results demonstrate that analyses based on time-independent power laws can obscure the distinction between transient and asymptotic corrosion behavior and that the TDPW formulation provides a physically consistent framework for interpreting corrosion kinetics in molten carbonate environments.
