Friction-induced stick-slip intensified by corrosion of gray iron brake disc

The effect of brake disc corrosion on friction-induced stick-slip was studied to find the possible causes of friction instability in humid conditions. The friction and wear characteristics of gray iron discs and a commercial friction material were examined using a 1/5 scale dynamometer. Use of the corroded discs resulted in a higher friction coefficient, and a larger oscillation amplitude of the brake torque. Disc corrosion increased the critical velocity showing transition from steady sliding to stick-slip. This suggests a rapid increase of the initial static friction coefficient as a function of dwell time in a humid condition, which is supported by the increased hydrophilicity of the friction films. The contact stiffness of the friction material surface was increased after rubbing with corroded discs, due to densification of the friction films by iron oxide nanoparticles transferred from the disc surface. The wear rate of the friction material also increased with corrosion of the gray iron discs.