Dynamic measurements of corrosion rates at high temperatures in high electrical resistivity media

An Acoustic Microbalance Study of High-Temperature Naphthenic Acid Corrosion of Common Iron-Alloying Elements

“…8 Each experiment was repeated a minimum of two times to assess reproducibility, and in all cases the experimental deviations were less than 10%. To calculate the corrosion rate, the method of Lu and Lewis was applied, 13 in the same manner as in previous work, 8 utilizing the density and acoustic impedance of the element under investigation. Curve fitting was performed using a Savitzy-Golay filter in Origin 9.0 † to reject noise in the experimental data.…”

“…14 Fourier transform infrared spectroscopy (FTIR) studies were performed using the same method as reported in previous papers. 8,12 Additional experiments were conducted to determine the NA corrosion behavior of bulk samples that were stripped of their surface oxides in situ. The tests were conducted on macro-sized samples and the extent of corrosion was investigated by observations in a SEM.…”

“…25 As already mentioned, it was reported in an earlier study that NA corrosion of iron initiates by pitting of iron's airformed oxide film. 8 The same mechanism might be active for NA corrosion of stainless steel, where dilute concentrations of molybdenum in the alloy are able to stifle pit growth and thereby provide improved resistance to NA corrosion. 13 To ascertain whether air-formed molybdenum oxide is responsible in whole or in part for molybdenum's resistance to NA corrosion, the surface oxide was removed in situ from a sample of molybdenum.…”

“…In an earlier investigation, the GPCM test of iron was interrupted at various times, and the sample was examined in a SEM for evidence of corrosion. 8 The results indicated that during the first 15 min of exposure to 3 wt% NA, the air-formed oxide is etch pitted. With increasing time of exposure, the pits propagate through the thickness of the oxide.…”

“…Recently the authors reported the use of a gallium orthophosphate crystal microbalance (GPCM) to measure the instantaneous corrosion rates of iron in laboratory-simulated crude at 270°C. 8 GPCM has the potential to provide precise, time-dependent measurements of corrosion rate and, in combination with microscopic observations of corroded surfaces, can help to identify mechanisms of corrosion in crudes and other high electrical resistivity media over a wide range of temperatures.…”