Climate friendly energy and mobility are major challenges of the industry. Polymer-electrolyte-membrane fuel cells (PEMFC) are a versatile technology in order to minimize CO₂ emissions. The bipolar plate (BPP) is an important component of a fuel cell, since it is responsible for the distribution and removal of the process media, electrical connection, cooling and stability. Therefore, the BPP must have good electrochemical, electrical and mechanical properties, i.e. high corrosion resistance, low resistance and high strength. Physical vapor deposition, especially cathodic arc evaporation, is an appropriate technology for applying specific surface modifications in order to enhance the necessary properties.

Austenitic stainless steel (SS316L) is an excellent suitable material because of its good formability, weldability, strength and corrosion resistance. However, due to the native oxide layer the electrical resistance is too high for the application. Additionally, in the harsh fuel cell environment the stain-less steel is susceptible for corrosion. Consequently, a conductive and protective surface modification is required. Therefore, we develop a carbon-based coating by cathodic arc evaporation as surface modification onto SS316L substrates. Hereby, the influence of the deposition temperature, which can significantly affect the properties of a PVD coating, was investigated. It was found that the electrochemical and electrical properties of the SS316L substrate are considerably improved. Mainly the corrosion resistance is affected by the deposition temperature. There are only minor differences in the contact resistance between the different coatings and they are highly conductive. Material analysis by Raman spectroscopy revealed that the coatings likely exhibit a graphite-like carbon or nano-crystalline structure.