The Characterization of Metal Soaps

Abstract

To characterize more fully the metal soaps found in paint films or on metal surfaces, several metal soaps were synthesized and their X-ray diffraction pattern and Fourier transform infrared (FTIR) and Raman spectra measured. Metal soaps were obtained from four different fatty acids found in drying oils — two saturated (palmitic and stearic acids) and two unsaturated (oleic and linoleic acids) — and from copper, zinc and lead, three metals that are typically found in metal alloys and paint systems. Data are reported for the following compounds: palmitic acid, stearic acid, oleic acid, linoleic acid, zinc palmitate, zinc stearate, zinc oleate, zinc linoleate, copper palmitate, copper stearate, copper oleate, lead palmitate, lead stearate and lead oleate. Features that are characteristic of specific compounds were observed. Soaps obtained from different fatty acids with the same metal ion show differences, as do soaps obtained with the same fatty acid but with different metal ions. Identification is key to understanding how and why metal soaps form on actual objects, and this may lead to preventive measures.