Filiform Underfilm Corrosion of Lacquered Steel Surfaces

Abstract

IN the course of some work on the corrosion of steel plate surfaces coated with transparent oil-modified synthetic lacquers in atmospheres containing acetic acid and water vapour, the production and growth of the hair-like corrosion tracks known as 'underfilm corrosion' were observed under the microscope. It has been suggested that these corrosion tracks follow cracks in the oxide film separating the metal and the lacquer. The samples were prepared by cutting grids of one inch mesh through the lacquer coating with a razor blade. These were then exposed in a desiccator with a dish containing 5 per cent acetic acid for 24 hours, after which the acid solution was replaced by water.