Healing performance of epoxy coatings

The effects of the healing agents' molecular characteristics on the self-healing performance of the epoxy coatings were studied via corrosion evaluation techniques. Methylene diphenyl diisocyanate (kept constant) and different polyetheramine healing agents were encapsulated separately in poly(styrene-co-acrylonitrile) through the electrospray method and added to the epoxy matrix to prepare a polyurea-based dual capsule extrinsic healing system. Commercial grades of polyetheramine, Jeffamine D230, Jeffamine D400, and Jeffamine T403, were used to study the effects of molecular weight and functionality.

Adverse effect on the corrosion protection ability

Electrochemical Impedance Spectroscopy (EIS) was employed to monitor the corrosion behaviour of a series of coated carbon steel samples with scratched coatings at different exposure times in a near-neutral 3.5 wt% NaCl solution. The results revealed the adverse effect on the corrosion protection ability by increasing the healing agent's molecular weight, while an increase of its functionality improved the final healing efficiency of the coating. According to the EIS results, the maximum healing efficiency was determined to be 85%, 72%, and 90% for Jeffamine D230, Jeffamine D400, and Jeffamine T403, respectively.

The study has been published in Progress in Organic Coatings, Volume 159, October 2021.