To gain insight into the processes of transformations in zero-valent iron systems, electrolytic iron (El) has been used as a surrogate for the commercial products actually used in barriers. This substitution facilitates mechanistic studies, but may not be fully representative of all the relevant processes at work in groundwater remediation. To address this concern, the kinetic iron model (KIM) was used to investigate sorption and reactivity differences between El and Connelly brand GI, using TCE as a probe compound. It was observed that retardation factors (R-app) for GI varied non-linearly with influent concentrations to the columns (C-o), and declined significantly as GI aged. In contrast, R-app values for El were small and insensitive to C-o, and changed minimally with iron aging. Moreover, although declines in the rate constants (k) and increases in the sorption coefficients were observed for both iron types, they were most pronounced in the case of El. SEM scans of the El surface before and after aging (90 days) established the appearance of carbon on the older surface. This work provides evidence that iron with a higher surface carbon content outperforms pure iron, suggesting that the carbon is actively involved in promoting TCE reduction. (C) 2017 Elsevier B.V. All rights reserved.