Water uptake in a water-borne paint: a supported and free film comparison

Paints behave as barriers to protect the metallic substrate against corrosion. In the present work, the water uptake in an acrylic water-borne paint was studied under two different conditions: supported and free film, immersed in a sodium chloride 5% solution. Using the impedance spectroscopy (IS) technique, a sharp increase in the film capacitance was observed, which is related to the volume fraction of water taken into the film by using the Brasher-Kinsbury equation. The results suggested that there was no big differences between both situations. The calculated apparent diffusion coefficient suggest that the difference between both tested situations is of minor importance. (Author) 17 refs