INVESTIGATION OF THE WEAR BEHAVIOR OF TYRE STEEL CORDS USING ELECTROCHEMICAL METHODS

The goal of our investigations was to characterize tyre steel cords of different constructions according to their wear behaviour by measuring some corrosion parameters in dilute K2SO4 as electrolyte. The wear tests were performed using Hunter-type machines, where the probes with a length of 29.6 cm are fixed at one end by a guide hole and the other end is placed in a drilling jig. This drilling jig rotates with a definite velocity for different times (from 1 to 24 h). The effect of the fatigue on the corrosion behaviour of the steel cords was measured on single filaments of the same cords. During the rotation the cord filaments show characteristic wear damage, which can be measured using electrochemical techniques, such as the determination of the time dependence of the corrosion potential and of the corrosion current densities (using modified Butler-Volmer techniques). It was possible to show that the wear damage of steel cords depends strongly on the surrounding atmosphere during the Hunter treatment and on the construction of the steel cords. In an air or oxygen-containing atmosphere the cathodic reaction of the overall corrosion process is oxygen reduction. According to the large area of exposed surface, where oxygen reduction can proceed, the total corrosion reaction rate is high and, in relatively short times, visible corrosion products appear on some parts of the steel cord with wear damage of single filaments. We found highly negative corrosion potentials in relation to the untreated reference materials. In an argon atmosphere the corrosion reaction proceeds more slowly and we found more positive corrosion potentials, only small corrosion current densities and no significant wear damage.