Refined surface treatment technology brings new applications for metals
Surface treatment significantly enhances the durability and functionality of materials used in various industries. Plasma electrolytic oxidation(opens in new window) (PEO) has emerged as a cutting-edge technology in this field. By utilising high-energy plasma discharges, PEO not only improves corrosion and wear resistance on metal surfaces but also enables the integration of additional functionalities such as photocatalytic and magnetic properties. Funded by the Marie Skłodowska-Curie Actions programme, the FUNCOAT(opens in new window) project focused on innovative ways to improve PEO technology by particle addition. The main objective was to design, develop and scale up new PEO surface treatments to create coatings with multiple functions. These improved coatings were meant to solve key challenges such as protecting materials from corrosion, preventing fouling and offering antimicrobial properties. By adding special particles (including nanocontainers) and chemical compounds into the PEO treatment process, researchers sought to make these coatings more effective.
Turning porosity challenges into advantages
A unique aspect of the FUNCOAT project was tackling porosity issues in PEO coatings. “Porosity – tiny holes in the surface – is a natural side effect of the PEO process caused by the discharges that form the coating. While these pores often undermine corrosion resistance, they are an unavoidable byproduct of the process given that the discharges are essential for creating the coating,” explains Maria Serdechnova, project coordinator. “We explored how to use this porosity to our advantage, while maintaining the coating’s desired performance.”
Unlocking new, unexpected functionalities
“We sought to advance surface treatments by developing improved coatings that offer key benefits for industries such as transport, electronics and environmental protection. For the transport sector, the focus was on improving fault tolerance, active corrosion protection and wear resistance (tribological behaviour),” says Serdechnova. Researchers also explored new functionalities such as photocatalytic properties, magnetism and thermal or electrical conductivity to expand PEO treatment applications. To achieve their goals, the project team embedded functional particles and species directly into the PEO coating in a single step, bypassing the need for post-treatments. This method marked a significant departure from standard practices but posed a key challenge. Many functional materials, such as layered double hydroxides (LDHs) loaded with organic corrosion inhibitors, were highly sensitive to the heat and intense plasma discharges during the PEO process. This led to their decomposition and prevented their original functions from being effective in the coatings. “Surprisingly, the decomposition of these particles had also positive effects. For instance, when LDH particles were introduced, their breakdown resulted in a foamy ceramic structure on the coating that significantly enhanced its photocatalytic properties,” outlines Serdechnova. “While this outcome was less effective for corrosion protection, it opened the door to new possibilities for applications in areas like environmental cleaning.” To address the challenges posed by sensitive particles and compounds, researchers made specific adjustments to the PEO process design and control over the energy input. They also proposed new designs such as silicon shells, LDH nanocontainers, magnetic materials and photoactive compounds to functionalise the developed coatings. These innovations pushed the boundaries of PEO technology, paving the way for coatings with multifunctional properties tailored to the diverse needs of industries.
