Requirements for corrosion inhibitor release from damaged primers for stable protection: A simulation and experimental approach using cerium loaded carriers

In this work a diffusion-driven inhibitor transport model is used to help in the design of inhibitor-loaded carriers for anticorrosive primers. The work focuses on inhibitor release at damaged locations of different dimensions exposed to electrolyte and is validated experimentally. The damage dimensions are first simulated to determine the minimal inhibitor release rate necessary to reach the required inhibitor concentrations for corrosion protection of the exposed metal. Kinematic and mass conservation laws are then used as first-order approximations to study the effect of different characteristics of nano- and micro-particles loaded with inhibitors embedded in an organic coating during the first 100 s of immersion. The simulated results are validated experimentally using epoxy coatings containing cerium-loaded zeolites and diatomaceous earth as nano- and micro-carriers respectively. These experiments confirmed the simulated predictions, showing that under the used exposure conditions nano-particles are only able to protect relatively small damages of micron size dimensions. Micron-sized carriers on the other hand allow sufficient release to protect larger damages, even at lower pigment volume concentrations. Additional simulations on rapid electrolyte diffusion pathways inside the coating are also in good agreement with the experiments, indicating the presence of diffusion pathways might play an important role in sustained inhibitor release and corrosion protection at local damages.