Electrospun protective self-healing coatings for light alloy: a better understanding of the intrinsic potential of the technology.

Polymeric coating systems exhibit high potentiality to provide an effective barrier against corrosion of metallic surfaces. However, these coatings can lose their protective characteristics due to their high susceptibility to damage. Thus, the addition of corrosion inhibitors is desirable and considered as an alternative route for active corrosion protection. In the present work, eco-friendly electrospun coatings of poly(vinyl alcohol) (PVA) loaded with cerium salts have been deposited onto aluminium 6082 alloy. Two different precursors of cerium (III) (i.e., cerium nitrate and cerium acetylacetonate) were added to the electrospinning solutions and the effectiveness of the resulting nanofibrous coatings was evaluated for the healing of generated defects. The microstructural features of the electrospun coatings have been investigated by scanning electron microscopy, infrared spectroscopy and thermal analysis. Tensile tests were performed to assess the mechanical properties of the different fibrous coatings. The electrochemical behaviour of both intact and damaged coatings was evaluated in 3 wt% NaCl solution by means of electrochemical impedance spectroscopy. All the deposited PVA coatings loaded with cerium (III) salts showed remarkable corrosion resistance. In the case of artificially damaged coatings, a self-healing effect, which stops the development of the corrosion process and provides a significant recovery of the corrosion resistance, has been observed only for coatings loaded with cerium III acetylacetonate. The release of cerium from damaged PVA fibers has been demonstrated by means of inductively coupled plasma mass spectrometry. The observed self-healing effect has been ascribed to the formation of cerium hydroxide on the defective zone, which hindered the corrosion process.