In this paper, the effect of gradually increasing amounts of KMnO4 (10-4, 10-3, 10-2 mol·L-1) in cement paste on the bond strength of a plain hot-dip galvanized steel bar was evaluated. The open-circuit potential of HDG samples in cement paste with various additions of MnO4- was monitored in order to follow a transfer of zinc from activity to passivity. Furthermore, the influence of the addition of these anions on the physicochemical properties of normal-strength concrete or cement paste was evaluated by means of hydration heat measurements, X-ray diffraction analysis, and compressive strength. The effective concentration of MnO4- anions prevents the corrosion of the coating with hydrogen evolution and ensures that the bond strength is not reduced by their action, which was determined to be 10-3 mol·L-1. Lower additions of MnO4- anions (10-4 mol·L-1) are ineffective in this respect. On the other hand, higher additions of MnO4- anions (10-2 mol·L-1), although they ensure the corrosion of the coating in fresh concrete without hydrogen evolution, but affect the hydration process of the cement paste that was demonstrated by slight water separation.
Keywords: bond strength test; concrete; corrosion; hot-dip galvanized steel; permanganate.