TGA–FTIR study of the vapors released by triethylamine–acetic acid mixtures

Proprietary mixtures of amines and carboxylic acids are used as volatile corrosion inhibitors (VCIs) for the protection of iron and steel components against atmospheric corrosion. This study was focused on the nature of the vapors they release. VCI model compounds comprising mixtures of triethylamine and acetic acid were studied using thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TGA–FTIR) at 50 °C. As vaporization progressed, the composition of the remaining liquid and the emitted vapor converged to a fixed amine content of ca. 27 mol%. This was just above the composition expected for the 1:3 amine to carboxylic acid complex. Mixtures close to this composition also featured the lowest volatility.