On the electrochemical response and interfacial properties of steel-Ca(OH)2 and the steel-concrete system measured using galvanostatic pulses

The interfacial properties of the steel-concrete system are examined via a new approach for evaluation of galvanostatic pulse data. This methodology allows for rapid determination of the corrosion activity of steel, and readily yields values for parameters related to corrosion such as the polarisation resistance and interfacial capacitance. The method of analysis is based on the iterative fitting of a non-exponential model based on a modified Kohlrausch-Williams-Watt (KWW) formalism. The transient behaviour of steel in concrete is non-exponential in its form and, when analysed this way, an exponent β can be determined characterising the exponential non-ideality of the transient. This non-ideality parameter is found to differ significantly for actively corroding and passive specimens, thereby serving as a useful index to the level of corrosion being experienced. Furthermore, the investigation of the interfacial characteristics of the system, previously unobtainable in a reproducible manner via other electrochemical methods, reveal information regarding the kinetic factors governing corrosion of steel in concrete.