A NEW TREND FOR STUDYING THE EFFECTS OF RUBBER RESISTIVITY ON THE CORROSION RATE OF STEEL CORDS IN RUBBER/STEEL COMPOSITES

Leakage of rubber adhesion for all steel cords surface is the main cause of corrosion. The corrosion occurs by moisture which may penetrate through microgaps along the steel cords in the tire bead ply and other rubber composites e.g., steel belts ply. In this paper, a new trend is used to study the effects of electrical resistivity of the rubber compound which shows galvanic corrosion cell with steel cords, in such a way that rubber behaved as a cathode and steel as an anode, and this mechanism is called galvanic coupling corrosion. The study shows that rate of corrosion is mainly affected by electrical resistivity of rubber (rho). When the resistivity is high rho > 10(4) Omega.m, corrosion is suppressed. If resistivity is very low rho <10(2) Omega.m, corrosion is greatly amplified and is extremely fast, and if resistivity is at the intermediate 10(2) Omega.m < rho < 10(4) Omega.m, a short-term activation of the steel corrosion is initiated. For this purpose, some grades (23 grades) of carbon blacks (CBs) are used as fillers in natural rubber (NR) with different loading levels. Sequence of such study shows that corrosion rate is mainly affected by rubber resistivity rho, where the resistivity rho is depending greatly on the grade and amount of carbon black. Those 23 types represented most groups of CBs could give clear map for using specified CBs in most compounds-based rubber.