Electrochemical demolition as a high-productivity and eco-friendly recovery process of hardmetal scrap

This work investigates the optimization and mechanistic understanding of Pulsed ElectroChemical Demolition (PECD) for the recycling of WC-based hardmetal grades with different binder chemistries and microstructures. The study focuses on three representative hardmetals, namely a coarse-grained Co-rich WC–Co grade (G1), a fine-grained Cr-alloyed WC–Co grade (G2), and a Ni-based WC–Ni grade (G3). Electrochemical demolition experiments were carried out in acidic sulfate electrolyte under both potentiostatic and galvanostatic pulsed conditions, using hanging-meniscus and immersed-electrode configurations. The process alternates low-anodic polarization, promoting selective binder dissolution and pseudopassive layer formation, with high-anodic polarization, where oxygen evolution mechanically removes the poorly conductive corrosion products and reactivates the surface. The optimized potentiostatic process enabled demolition rates up to 38 mg cm⁻² h⁻¹, comparable with a typical thermal demolition rate of 64 mg cm⁻² h⁻¹ for the Co-rich grade, while maintaining effective separation between tungsten-containing solid products and dissolved binder species. Electrochemical transient analysis demonstrated that, despite quantitative differences related to binder composition and corrosion resistance, all investigated grades follow a common pseudopassivation/reactivation mechanism. Immersed-electrode experiments confirmed the robustness of the process under less homogeneous current-density distributions, while galvanostatic operation demonstrated the feasibility of simplified industrial implementation. Morphological and compositional characterization showed that the solid demolition products mainly consist of WO₃-rich porous fragments containing residual WC, with tungsten purity close to 99.6 wt%. Overall, the results demonstrate that PECD represents a scalable and environmentally sustainable alternative to conventional pyrometallurgical hardmetal recycling, combining high demolition productivity with effective separation of critical raw materials.