Welding Technologies for Metallic Bipolar Plates in Proton Exchange Membrane Fuel Cells: A Critical Review of Processes, Joint Performance, and Manufacturing Readiness

Abstract

Metallic bipolar plates (BPPs) enable thin, lightweight, and high-throughput proton exchange membrane fuel cell (PEMFC) stacks, but their industrial value depends on joining two formed foils without sacrificing gas tightness, dimensional accuracy, electrical performance, or corrosion durability. This article presents a critical narrative review of welding and related joining technologies for metallic BPPs. Literature was evaluated through 31 July 2026 and interpreted using three evidence levels: direct validation on BPP assemblies, BPP-relevant thin-foil analogue studies, and transferable evidence from general microjoining. Laser welding has the strongest combined evidence because it offers localised heat input, high path flexibility, and compatibility with automation; however, its process window is narrowed by foil thickness, inter-sheet gap, variable heat sinking, coating condition, and high-speed melt-flow instabilities. Resistance seam welding provides direct evidence of leak-tight stainless-steel BPP joining and may be attractive where two-sided electrode access is available, although electrode wear, indentation, and complex-path capability require closer attention. Published BPP-specific validation of tungsten inert gas/microarc, electron-beam, ultrasonic, friction-stir-based, brazing, and adhesive routes remains insufficient for claims of high-volume readiness. Across all processes, the most consequential unresolved issues are the absence of harmonised seam-leak qualification, limited long-term fatigue and weld-zone corrosion data, uncertain welding-coating process sequences, and the lack of representative public datasets for in-line quality prediction. A qualification framework is proposed that links process parameters and weld morphology to mechanical, sealing, electrical, electrochemical, and durability outcomes. The review concludes that future progress depends less on isolated peak weld strength than on full-plate robustness, traceable defect detection, coating-aware process integration, and statistically demonstrated manufacturing capability.