Naphthenic acid, a significant cause of corrosion of carbon-steel in crude oil, has been investigated at elevated temperatures using vibrational spectroscopic methods (Raman and Fourier transform infrared (FT-IR)). Unlike earlier reports of studies at ambient temperatures, these elevated temperature experiments performed on a series of carboxylic acids having structures similar to naphthenic acid components in crude oil and on a commercial naphthenic acid mixture show a progressive increase with increasing temperature in the concentration of monomer over the multimers, which drives the formation of iron naphthenate. This observation forms a reasonable basis for proposing a mechanism of corrosion in crude oil at temperatures closer to the boiling point of naphthenic acids, which proceeds through the acid monomer.

The films that form on pure iron during potentiodynamic anodic polarization in aqueous borate buffer were investigated by surface enhanced Raman spectroscopy (SERS), and by electrochemical impedance spectroscopy and Mott–Schottky analysis at selected potentials. According to SERS, the passive film is a bilayer film with an outer layer of an as yet undetermined Fe(III)oxide/hydroxide, identified by a strong Raman peak at 560 cm−1. The inner layer was a spinel compound. The capacitances of passive iron were frequency dependent and a constant phase element (CPE) best described the frequency dispersion. Current increases in cathodic polarization scans confirmed the accuracy of flatband potentials calculated from Mott–Schottky tests at two different film formation potentials. Both films were found to be n-type and flatband potentials of −846 and −95 mV vs. SHE and carrier densities of 1.6 × 1022 and 8.3 × 1020/cm3 were found for films grown at −500 and +1000 mV, respectively. The cathodic polarization curve of passivated iron exhibited a complex shape that was explained by the electronic properties of iron's passive and prepassive films. The reductive dissolution of the films abruptly began when the potential was lowered below their flatband potentials. It is suggested that the cathodic polarization behavior contributes to iron's susceptibility to localized corrosion.

The as-grown structure of electrochemically synthesized titania nanotubes is investigated by a combination of cross-sectional and high-resolution transmission electron microscopy (TEM). The analysis reveals a preferred growth direction of the nanotubes relative to the substrate surface and the presence of a thin barrier oxide layer that exists between the metal substrate and the nanotubes. High-resolution TEM images also provide information about the morphology of the metal/oxide and oxide/nanotube interfaces, and the crystallinity of the different layers. In addition, compositional analysis performed via energy dispersive X-ray spectroscopy (EDS) indicates that there are differences in oxygen and titanium concentrations between nanotubes and barrier oxide. The experimental observations obtained from these analysis techniques provide additional insights about the tube formation process.