Mechanochemical activation of zinc powder via open-circuit potential for coatings

This study systematically investigates the adhesion mechanism of zinc powder in the wet mechanical plating process. A multidimensional characterization system integrating open-circuit potential (OCP), morphological features, and dynamic behavior was established. This system combines real-time OCP monitoring, high-speed imaging, and scanning electron microscopy (SEM) to enable in situ analysis of the zinc powder adhesion process on iron/zinc substrates. The results demonstrate that the dynamic OCP response effectively characterizes the synergistic interaction between activators and adhesives. Specifically, activators disrupt the passivation layer on the zinc powder surface by generating an acidic microenvironment, whereas adhesives induce plastic deformation of the zinc powder by modulating the solution rheology. Interfacial micromorphology analysis reveals that both the surface roughness of the zinc powder and the substrate surface energy jointly determine the mechanical interlocking strength. Mechanistic investigation confirms that the adsorption process follows a three-stage “activation–adhesion–interlocking” model. Initially, acidic activators remove the ZnO layer; subsequently, Sn-bearing structures form on the zinc powder surface under the action of a stannous sulfate adhesive; finally, mechanical interlocking is achieved through stochastic collisions that induce geometric adaptation. The proposed “potential–morphology–kinetics” correlation model provides a theoretical foundation for the development of mechanical plating processes, particularly for mechanically deposited aluminum and titanium coatings. Furthermore, it offers experimental support for applying the “making materials plain” concept in metal powder-based surface modification.