Self-diagnosing and active protective dual-functional water-borne polyurethane coating based on smart mesoporous containers

In this work, a dual functional coating was constructed to possess self-diagnosing and active anti-corrosion protection using pH-sensitive mesoporous silica containers containing gallic acid (GA). The containers are capable of releasing the inner GA when corrosion occurs at the metal substrate/coating interface due to pH sensitivity. GA can react with the Fe3+ ions to form conspicuous purple color at damaged sites, which provides the coating with a fast and timely corrosion self-diagnosing function. It can also inhibit the expansion of corrosion and realize active corrosion protection. This work provides a new idea for the multifunctional design of smart coatings with a single substance that provides both self-diagnosing and active corrosion protection.