An investigation on the corrosion of brass-coated steel cords for tyres by electrochemical techniques

Abstract

The electrochemical behaviour of brass-coated steel cord and brass-coated steel wire in a 0.25 M Na 2SO 4 solution has been studied by variation of the corrosion potential with immersion time in the aggressive solution and by determination of current–voltage curves and electrochemical impedance measurements. A corrosion mechanism of brass-coated steel wires that relies on a zinc depletion process of the brass coating and on the development of a copper oxide film over the zinc-depleted brass layer has been proposed in agreement with surface analyses (photoelectrons spectroscopy). The cord appears to be more resistant to corrosion than the wire. The hypothesis has been put forth that the zinc depletion process starts later and advances at a lower rate in the cord than in the wire. As far as the electrochemical techniques are concerned, electrochemical impedance spectroscopy allows the corrosion resistance of the two systems to be evaluated.