Electrochemical characteristics and damage behaviour of DLC-coated 316L stainless steel for metallic bipolar plates of PEMFCs

A diamond-like carbon (DLC) coating was deposited on the surface of 316L stainless steel using the arc ion plating (AIP) method to improve the life and efficiency of the metallic bipolar plate for polymer electrolyte membrane fuel cells (PEMFCs). The electrochemical characteristics and damage behaviour were investigated in an accelerating solution simulating the PEMFCs operation environment. A result of the experiment showed the corrosion current density of all specimens with DLC coatings was lower than that of the base metal. However, when the thickness of the DLC coating was 0.3 and 0.5 μm, the corrosion resistance was lower than that of the base metal. This is thought to be because defects on the coating surface result in crevice corrosion of the gap between the coating layer and the intermediate layer or between the coating layer and the base metal, further accelerating corrosion.