The Use of 3D-Svet for the Examination of Plasticised PVC Coatings: The Effect of Deformation and UV Irradiation on Barrier Properties
The model study demonstrated that both the planar non-irradiated and the planar irradiated samples retained their coating integrity, with the 3D SVET detecting no corrosion activity during a 24hr immersion study. In contrast, the samples that underwent a forming process showed evidence of a cathodic band of activity that coincided with the peak of the bend. This band increased in activity during the period of immersion, most likely due to the improved oxygen availability at the thinnest part of the coating. Findings from the industrial coating (See Fig 1A-C) showed the presence of numerous penetrative defects and it was found that the majority of the longer lived defects existed within the emboss pattern, coinciding with thinnest part of the coating. Subsequent removal of the industrial coating evidenced the extent of the zinc dissolution that occurred during the samples lifetime.
Figure 1: A) The surface profile of the industrial coating, illustrating the leathergrain emboss pattern within the paint. B) A Surface image of the coating overlaid with the most active anodic areas as measured over 24hrs immersion in 5% NaCl. C) The resulting galvanneal surface post removal of the plastisol coating, illustrating the metal dissolution during the samples life.