Naphthenic Acid Corrosion: The Effect of Phosphorous and Non-Phosphorous Inhibitors on Carbon Steel Surfaces

Naphthenic acids present in crude oils contribute to high temperature corrosion.  Corrosion caused by naphthenic acids generally occurs in the temperature range of 400-750 °F.  The use of corrosion inhibitors is a common mitigation strategy.  Phosphorus based compounds are known to be effective in naphthenic acid corrosion control.  However, industrial specifications have enforced limitations on phosphorous content and lead to the need for phosphorous-free replacements.  In this context a systematic surface study of carbon steel surfaces exposed to both phosphorous and non-phosphorous based corrosion inhibitors is proposed.
Characterization of the untreated and treated carbon steel specimens was approached via X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) spectroscopy.  In addition, morphological data were obtained using a super-resolution Vertical Scanning Interferometry (VSI) technique.  Molecular modeling was used to correlate electronic properties relevant to their reactivity.  
Keywords: naphthenic acid, corrosion inhibitor, carbon steel, XPS