Toward a Corrosion Proof Braking System

The manuscript firstly overviews the corrosion potentials of several components used in disk-brake systems. Particular attention is devoted to the couplings between materials with different nobility. It is demonstrated that if two materials: a) show a difference in their corrosions potential (E_corr) >100mV; and b) are in electric contact in the presence of an electrolyte; they can form a galvanic couple (GC) which could undergo severe corrosive phenomena. In the second part, the paper focuses on the anodized Aluminium (ANOD-Al)-stainless steel (SS) GC. This couple is investigated since: 1) anodized Al and SS are often comprised in high-end braking systems and typically constitute the caliper body (anodized Al) and several components (springs, pins, screws, metal plates, rods, shims etc.) included; and 2) it shows one of the largest corrosion potential difference among all materials included in a braking system (>500mV). As a consequence, the ANOD-Al-SS appears to be one of the most strategic GC whose careful electrochemical investigation will allow the development of future corrosion-proof braking systems. Addressing this point, the manuscript investigates the effect on the corrosion rate of the distance (d) and the area ratio (A_ratio) between anodized ANOD-Al and SS components using a suitable model system. This approach allows for the first time to obtain design rules based on the corrodibility of different materials with the final aim of customizing the corrosion protection of each brake system component.