‘Smart’ corrosion inhibiting coatings

Under certain conditions, the driving force of corrosion produces protective oxide films, a process typically referred to as passivity. In cases where passivity is difficult to achieve, for example, for Al alloys in neutral NaCl solutions, it is conceivable that a ‘smart’ coating can be micro- or nano-engineered to use the energy of the corrosion to generate ‘on demand’ a corrosion inhibitor for stopping or slowing corrosion at defects. Work at Rockwell Scientific provides evidence that anionic inhibitors for the oxygen reduction reaction (ORR), when used as dopants for conducting polyaniline (PANI) films, inhibit corrosion of a Al 2024-T3 substrate at a scribe. In effect, the scribe polarizes the PANI causing it to release the inhibitor.