The Factors Governing the Corrosion Stiction of Brake Friction Materials Against a Gray Cast Iron Disc 2018-01-1899
Corrosion stiction at the contact interface between brake friction materials and gray iron discs under the parking brake condition was investigated. Various possible parameters to affect the shear force to detach the interface at the onset of motion after corrosion stiction were evaluated to find the root causes of the fastidious brake problem. Using commercial brake friction materials, comprising non-steel and low-steel types, corrosion tests were carried out by clamping the pads against gray iron discs at different experimental conditions. Results showed that the shear force to detach the adhered interface increased with applied pressure, temperature, corrosion time, and humidity. On the other hand, acidity (pH), porosity, and hydrophilicity of the friction material did not show reliable correlation to the shear force, suggesting that the corrosion stiction was determined not by a single factor but governed by multiple parameters, which were determined by the type of ingredients used in the brake friction material. Microscopic analysis of the cross section of the adhered interface was in-line with the multifaceted nature of the corrosion stiction. Another salient feature of this study was the finding that the shear force was well correlated to the electrochemically measured corrosion rate of the gray iron discs in the solution prepared by dissolving the friction material on the water, suggesting that the electrochemical corrosion test can be a viable alternative to estimate propensity of corrosion stiction of the brake friction material.
Jaehyun Gweon, Sanghee Shin, Ho Jang, Wangyu Lee, Dooyeon Kim, Keeyang Lee