Toward a New Generation of Organic Coatings for Corrosion Protection Based on Poly(phenylene methylene)

Metal corrosion is a costly surface phenomenon that is typically prevented by organic coatings based on cross-linked resins. However, these coatings have severe limitations in recycling, and small defects are difficult to detect and repair, which can lead to hidden corrosion and catastrophic material failure. Modified poly(phenylene methylene) (PPM) coatings overcome these shortcomings because they are thermoplastic and recyclable and can be customized by incorporating functional additives or through side chain engineering, resulting in self-healing and fluorescent coatings for straightforward, on-demand, and nondestructive quality control over the entire time range from application to service life. Furthermore, the use of PPM-based polymers might eliminate the need for surface pretreatments, which are commonly performed to improve coating adhesion. To date, however, PPM-based corrosion protection has only been validated on a single yet significant aluminum alloy (AA2024). Broadening its applicability to other metals/alloys, exploring powder coating techniques, and enhancing glass transition temperatures while retaining self-healing functionality are key directions for future research.