Influence of calcium cations on the corrosion behavior of hot-dip galvanized steel in model concrete pore solutions

Abstract

In this paper, the influence of calcium cations on the corrosion behavior of hot-dip galvanized steel in model concrete pore solutions is evaluated by means of conventional electrochemical methods (measurement of free corosion potencial and polarization resistance), surface analysis methods (optical and confocal microscopy) and XRD phase analysis of precipitated corrosion products. The results of these experiments confirm the conclusions of the current work on a similar topic, i.e. the crystalline calcium based corrosion products Ca[Zn(OH)3]2·2H2O are not able passivate effectively surface of hot-dip galvanized steel in model of concrete pore solutions (pH 12.6; 13.0). If passivation occurs, a mixed Ca[Zn(OH)3]2·2H2O, ZnO and Zn(OH)2 is involved.

Kinetics of Zinc Corrosion in Concrete as a Function of Water and Oxygen Availability

“…The ratio of ZnO in corrosion products is negligible. This kind of experiment can also confirm the negative effect of Ca 2+ on the evolution of the passive layer on zinc or galvanized rebar in model concrete pore solution [16,18] or in real concrete [17]. SEM images also confirm the presence of CHZ (Figure 10) [11,25].…”

“…Should the zinc probes lean towards passivation in concrete, a drop of corrosion rate and an increase of free corrosion potential in a positive direction would be observed in flooded concrete [5,17,18,23].…”

“…Using current measurement techniques, the efficient passivation capability was challenged [16,17,18]. One alternative theory suggests that the presence of Ca 2+ cations in model pore solution causes destabilization of the original amorphous layer of ZnO and Zn(OH) 2 , described in detail in alkaline solutions of similar pH (12.6–12.8); however, without Ca 2+ [19,20].…”