Laser surface modification on titanium bipolar plate for resistance enhancement of bonding interface to thermal and acidic corrosion

Abstract Adhesive bonding has become one of the joining and sealing technologies for titanium bipolar plates in proton exchange membrane fuel cells. However, the bonding interface of titanium bipolar plates is prone to fracture due to the effect of thermal-acidic environment inside the fuel cell, making it crucial to ensure the service stability of bonding interface. This study applied laser surface modification to addressing this challenge, and further investigated the effect of laser power and overlap ratio on the corrosion resistance of titanium bonding interface under thermal-acidic environment of 80 °C and 5 ppm fluoride ion. It is found that laser surface modification with higher overlap ratio fabricates deeper and denser pits on titanium surface, and with higher laser power generates complex dendritic structures around the pits. These factors effectively inhibit the degradation of bonding interface under corrosion in the thermal-acidic environment. The strength degradation was decreased to 18.9 % with residual strength maintaining above 20 MPa at optimal process parameters of 6 W power and 50 % overlap ratio. Additionally, the study revealed that corrosion temperature significantly affected the strength degradation of untreated joints, while caused negligible effect on the strength degradation of laser-treated joints. Higher temperature accelerated the diffusion of corrosive ions along the untreated interface, whereas the penetration of corrosive ions was prevented by laser-treated interface. Moreover, the dominant role of water was found for the degradation of titanium bonding interface.