Electrochemical behavior of zinc in alkali-activated fly ash solution

Abstract

To study the passivation process and chloride-induced corrosion mechanism of galvanized steel in alkali-activated fly ash (AAFA) solution, pure zinc was chosen as the working electrode. Moreover, two other simulated concrete pore solutions, e.g., saturated Ca(OH)2 solution and ordinary Portland cement (OPC) solution were also tested for comparative purposes. Based on various electrochemical measurements and surface characterization techniques, the passivation capability and the chloride-induced corrosion behavior of zinc and its critical chloride concentration were investigated. Although no calcium hydroxyzincate (CHZ) was formed for zinc in AAFA solution due to the lack of sufficient calcium ion, a zeolite-like adsorption layer as well as a silicate gel adsorption layer could be formed on the zinc surface. Accordingly, compared with the other alkaline solutions, enhanced corrosion resistance was evident for zinc in AAFA solution even in the presence of high chloride concentration. These findings of this study serve as the first step towards enhancing our understanding of the possible application of galvanized steel in alkali-activated materials exposed to harsh marine environments.