The cost of corrosion is estimated to be at least $276 billion per year in the United States alone.1 A 2001 study commissioned by the Federal Highway Administration analyzed 26 industrial sectors and found that direct costs accounted for approximately 3.2% of the U.S. economy. Often overlooked in these numbers are the costs related to equipment downtime. Time spent replacing or rehabilitating corroded equipment not only ties up valuable manpower, but also makes it necessary to maintain a reserve of excess capital equipment. With some service rotations as short as six months,2 even a modest increase in service life can lead to significant savings.
The most common approach to prevent corrosion is to paint the surface with a protective coating. Most paints have only limited ability to resist abrasion. Attempts to improve durability are ultimately constrained by the requirements that the coating be relatively thin (< 100 µm) and easy to apply. While repainting and touch-up can be performed as part of regular maintenance, many defects go unnoticed before significant damage occurs. Given that coating damage is inevitable, improvements in flaw tolerance may provide greater gains in corrosion protection than incrementally improved flaw resistance. To this end, we present self-healing coatings that autonomously repair scratches below a maximum width, delaying the onset of corrosion and increasing the time between maintenance cycles.