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

Abstract

This paper studies the effect of water as an oxidation agent and also of oxygen on zinc corrosion kinetics in active state in concrete, using high-sensitivity electrical resistance sensors. It was proven that zinc corrosion in active state is strongly affected by the presence of water at its surface. Zinc corrosion in real concrete in the absence of water can be misinterpreted as salt passivity. The presence of oxygen results in an increase of zinc corrosion rate, however at pH 12.6, passivity can occur. It was verified that corrosion products consisting primarily of Ca[Zn(OH)3]2·2H2O cannot effectively passivate zinc surface in concrete, even after 1800 h of exposure and zinc, or hot-dip galvanized steel can corrode at an unacceptable corrosion rate (more than 4 µm·a−1).

The Effect of Addition Potassium Permanganate on Bond Strength of Hot-Dip Galvanized Plain Bars with Cement Paste

“…The bond strength of the hot-dip galvanized plain bar with cement is clearly negatively affected by the hydrogen evolution during the initial corrosion reaction (see Equation ( 2)). As the released hydrogen increases the porosity of the cement paste at the phase interface [14,[20][21][22], the adhesion factor fad (evaluating the level of adhesion of the cement paste to the surface of the steel reinforce- The results of the ultimate bond strength for the reference samples (without KMnO 4 ) show a large variability in the data with an average value of 2.25 MPa. While this shear stress was read at the highest slip values (average value is around 0.1 mm) with respect to other groups of samples, it is evident that the hot-dip galvanized reinforcement shifts significantly during the load test in the cementitious mixture and the ultimate bond strength is reached at already relatively high slip values.…”

“…The eventual commercial use of hot-dip galvanized coatings for the same purpose has not reached the same scale as in the case of epoxy coatings. The reason for this is the still contradictory conclusions evaluating the effectiveness of this form of corrosion protection also with regard to the sustainability of the coating process and, of course, the effect on the load-bearing capacity of buildings [ 14 ].…”

“…In the case of exposure of HDG steel in simulated concrete pore solutions, an initial very intense corrosion attack occurs (anodic corrosion process of zinc oxidation is given as Equation (1)) under the evolution of hydrogen (cathodic corrosion process, see—Equation (2)) [ 6 , 8 , 9 , 14 ]. …”

“…Insoluble corrosion products are formed on the surface of the samples with the majority of Ca[Zn(OH) 3 ] 2 ·2H 2 O (ZnO/Zn(OH) 2 phases are also present) [ 6 , 8 , 9 , 14 , 15 , 16 ]. It is usually stated that mainly this phase (Ca[Zn(OH) 3 ] 2 ·2H 2 O—calcium hydroxyzincate—CHZ) conditions the transition of HDG steel active corrosion to the corrosion in the passive state (in the case of pH of model pore solutions up to 13.3 ± 0.1) [ 6 , 8 , 9 , 14 , 17 , 18 , 19 ]. The formation of Ca[Zn(OH) 3 ] 2 ·2H 2 O in model concrete pore solutions is described by the following Equations (3)–(5) [ 18 , 19 , 20 ]: …”

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

“…However, on this film of crystals, with an extended time, in the presence of chlorides, simonkolleite (Zn 5 (OH) 8 Cl 2 • H 2 O) and zincite (ZnO) eventually grow and become detectable, and this fact has been documented in the literature by long-term laboratory tests of specimens of zinc and galvanized steel after the pitting corrosion occurred (Belaid et al, 2000;Tittarelli and Bellezze, 2010;Zheng et al, 2018a;Román et al, 2014). In addition, in the long term, when there is no presence of chlorides, wulfingite (Zn(OH) 2 ) and zincite (ZnO) have been identified (Hegyi et al, 2017;Pokorný et al, 2017;Pokorný et al, 2019).…”