Evaluation of Resistance of Intermetallic Fe-Zn Coating in the Model Environment as Concrete Pore Solution

Effect of a Fast Potential Change on the Early Stage of Zinc Passivation in a Saturated Calcium Hydroxide Solution

“…In addition, it should be pointed out that some of the differences in the corrosion behavior of galvanized coating in concrete observed by different investigators are due to experimental differences, such as the water/cement ratio, quality of concrete, amount of cover, type of cement, aggregate, roughness of the coating surface, and metallurgical microstructure of the coating (Tan and Hansson, 2008;Pernicova et al, 2017). Several studies have been devoted to understanding the corrosion and passivation of galvanized coating in concrete and in simulated pore solutions, where, as a standard practice, the reference solution is the saturated calcium hydroxide solution, and the calcium ion has a major influence on the passivation of galvanized steel bars (Arenas et al, 2006;Sahoo and Balasubramaniam, 2008;Tittarelli and Bellezze, 2010;Dobias et al, 2017;Zheng et al, 2018a;Zheng et al, 2018b). Considering that the hot-dip zinc coating, described above, consists of iron-zinc alloy phases at the interface along with a top coat of pure zinc.…”

“…Two main mechanisms of passive film formation have been postulated: the "dissolution-precipitation" mechanism used for the interpretation of galvanostatic measurements and the "solidstate" reaction mechanism used for potentiodynamic measurements (Bockelmann et al, 2018). According to previous studies on the behavior of zinc and galvanized steel in fresh concrete, saturated calcium hydroxide solution, and simulated pore solutions, during first hours of immersion or embedding, occurs a spontaneous sudden change of potential from an active state to a passive state (Macías and Andrade, 1987a;Macías and Andrade, 1987b;Macías and Andrade, 1990;Zhang, 1996;Yeomans, 2004;Ghosh and Singh, 2007;Videm, 2007;Tittarelli and Bellezze, 2010;Dobias et al, 2017;Zheng et al, 2018b). However, as far as the authors know, there are no published reports about how fast the rate of change of such a sudden change of potential is and its effect on the type of passivating film formed during the early zinc passivation in calcium saturated or simulated pore solutions.…”