Morphology of copper corrosion under formic, acetic and propionic acid environment

The aim of this study is to investigate the effect of different types of an organic acid on morphology of copper corrosion. We conducted immersion and exposure tests of copper tubes using three types of an organic carboxylic acid; formic, acetic and propionic acid. Randomly-branched pores developed after immersion tests in the formic and acetic acid solutions. A layered corrosion occurred after the immersion test in 1000 ppm propionic acid solution. Ant nest corrosion was detected on the copper tube under the formic acid atmosphere, whereas a hemispherical pit was detected under the acetic acid atmosphere. A layered corrosion developed under the propionic acid atmosphere. SEM inspection and EPMA analysis revealed that constituents of the hemispherical pit developed under the acetic acid atmosphere were metallic copper with sponge-like pores and cuprous oxide infilled the pores.