TANTALUM-BASED COATINGS ON STAINLESS STEEL FOR FUEL-CELL BIPOLAR PLATES

摘要

Stainless steels are promising materials for fuel cell bipolar plates. It meets high demands for bipolar plates, good thermal and electrical conductivity, low cost, good mechanical properties. However, corrosion stability in fuel cell environment is either poor or achieved by passive layer. Passive layer improves corrosion resistance, but decrease electrical conductivity, respectively increase contact resistance. Coating stainless steel is one approach, how to obtain suitable material. This study focused on commonly used stainless steel AISI 316L as reference and two Ta-based coatings, tantalum coating and tantalum coating with upper layer of Ta_2O_5 and RuO_2. All materials were tested in simulated PEMFC environment, diluted sulfuric acid of pH 3 with 1 ppm fluoride ions at 80 °C . Open circuit potential, linear sweep voltammetry anodic and cathodic dynamic scans were carried out. Materials were compared only based on short-term electrochemical measurements. Despite that, tantalum coating performs better corrosion resistance than bare steel, passive layer of tantalum is non-conductive, thus inappropriate for fuel cells. Tantalum coating with oxide upper layer cannot be compared based on short-term electrochemical measurements.