Electrochemical Behavior of the Prestressing Steel in Alkaline Electrolytes: Influence of Chloride Ions

摘要

The paper presents the study on the electrochemical behavior of prestressing steel in alkaline electrolytes, with various levels of chloride concentration by using the cyclic potentiodynamic polarization technique. The electrochemical measurements were performed on two types of high-strength steel used as tendons for prestressed concrete: cold-drawn steel and thermally treated (quenched and tempered). The anodic potentiodynamic polarization curves of prestressing steel specimens in aqueous suspension of Portland cement CEM I (pH = 12.7) with 0.0001... 1.0 M [CI~-] were traced with a scan rate of 0.556 mV/s. The passivity breakdown (pitting) potential of steel was determined depending on the shape of the polarization curves, chloride ions concentration and type of steel. The obtained results allow the definition of a critical chloride ion concentration (chloride threshold) below which no prestressing steel depassivation occurs, with a value of 0.01 M [CI~-], respectively 0.0355% CI~- by mass of cement. The passivity breakdown (pitting) potential decreases linearly with the logarithmic values of chloride ion concentration. The potentiodynamic polarization method is a fast and efficient method for the comparative study of the influence of cements, additives and admixtures on electrochemical corrosion behavior of different types of prestressing steel in concrete.