Electrochemical Interpretation of the Corrosion Stiction of Brake Pads on the Gray Iron Disc

Corrosion stiction occurred at the interface between the brake pad and gray iron disc was investigated using commercial products. The corrosion test was carried out in an environmental chamber by clamping the pad and disc in a range of applied loads. Particular attention was given to the effect of the brake pad surface roughness on the corrosion stiction. The electrochemical reaction during corrosion was analyzed by measuring the corrosion rate of the gray iron disc loaded with the brake pads with different surface roughness. Impedance spectroscopy analysis was also performed to find the rate-controlling step of the corrosion stiction. The results showed that the size of the contact area, which was determined by the type of ingredients and braking condition, played a crucial role in the stiction force. The iron oxides produced by galvanic corrosion on the gray iron surface permeated to the tribolayers on the contact areas on the friction material surface and increased the adhesion of the brake pad to the disc surface. Understanding the electrochemical reaction during corrosion stiction allowed to find the rate-determining steps to reduce the corrosion stiction. The results also indicated that the size of the contact area on the friction material surface played a more prominent role in corrosion stiction than the composition of the friction material.