Self-healing properties of microencapsulated linseed oil-poly(urea formaldehyde) additives embedded polyester coating on Galvalume steel sheet

Linseed oil and poly(urea-formaldehyde)-based microcapsules with an 82% weight ratio of core/shell and a mean outer diameter of about 100 μm were synthesised by in-situ polymerisation. These microcapsules were dispersed in polyester paint and then primer-coated Galvalume sheets were painted with microcapsule loaded (MC) and neat (no microcapsules) paints. These painted samples were scribed and examined using various characterisation techniques to evaluate their self-healing properties. SST and CCT showed that the electrolyte diffusion was suppressed in the MC sample, whereas the neat sample was noticeably blistered due to under-film corrosion. Scanning Kelvin Probe microscopy, SKP supported this finding wherein the Volta potential of the neat sample increased in the positive direction indicating cathodic delamination, whereas no significant change occurred in the MC sample. SEM-EDAX revealed the surface morphology and composition of the samples. Furthermore, EIS showed that microcapsule addition increased the pore resistance and decreased the coating capacitance of the polyester paint.