Naphthenic Acid Corrosion Research Articles

Measuring naphthenic acid corrosion potential with the Fe powder test

Results are presented of experiments performed using a new method to measure the naphthenic acid corrosion potential. The method consists of adding pure iron powder into a small autoclave containing the crude or oil sample. The test is then performed at a given temperature for one hour, after which the oil sample is filtered and the remaining liquid is sent for iron content determination (ppm). The tests are run at 7 different temperature levels, 3 more are run as repeated tests. A best-fitted curve is drawn through these 10 experimental points and the maximum point is thus determined. This becomes the main outcome of the test and it is used to give a measure of the naphthenic acid corrosion potential. The same general trends as observed in the past using the neutralization number or TAN (Total Acid Number) is obtained. However, this new test seems capable oi detecting anomalous cases where oil samples having larger values of TAN exhibit less corrosivity than others having much lower values of TAN or where they show completely different corrosivity despite having similar or the same TAN.

Resistance of Mo-bearing stainless steels and Mo-bearing stainless-steel coating to naphthenic acid corrosion and erosion–corrosion

Naphthenic acid corrosion (NAC) and erosion–corrosion (NAEC) behavior of Mo-bearing (0–7.0 wt.%) stainless steels have been investigated in laboratory to evaluate the essential role of Mo on their NAC and NAEC resistance. The NAC and NAEC resistance of a high-velocity-oxygen-fuel (HVOF) thermal sprayed Mo-bearing stainless-steel coating was also investigated in both laboratory and an oil refinery. It was found that increasing the Mo content remarkably enhanced the NAC and NAEC resistance of stainless steels. The Mo-rich areas or phases in the steels played an importance role in resisting the NAEC. The HVOF coating showed excellent NAC and NAEC resistance in laboratory tests. The 700-day field test in an oil refinery revealed that the coating can effectively prevent the carbon-steel substrate from erosion–corrosion during long-term exposure in oil-refining environment. The corresponding NAC and NAEC mechanisms of the stainless steels and the beneficial role of Mo were discussed by taking account of inherent susceptibility of metal elements to corrosion, possible effects of Mo on surface films, and Mo-induced change in microstructure and microhardness.

Corrosion and erosion-corrosion behaviors of carbon steel in naphthenic acid media

The naphthenic acid corrosion (NAC) and erosion-corrosion (NAEC) behaviors of carbon steel were investigated detailedly in laboratory. The resistance to NAEC of pack-aluminized carbon steel and carbon steel coated by high velocity oxygen-fuel (HVOF) thermal-sprayed AISI 316L stainless steel, was also investigated in both laboratory and an oil refinery. It was found that the control-step of NAC was primarily dependent on the temperature. The NAC rate of carbon steel increased markedly with the increase of the total acid number and temperature, which may be attributed to the enhanced absorption and active reaction of naphthenic acid molecules on the metal surface. Increasing the velocity of flow seriously aggravated NAEC, especially in the high temperature range. The reasons were closely associated with the enhanced mass transfer and the accelerated active reaction as well as the rapid spallation of corrosion products from the metal surface. Both the aluminized carbon steel and the carbon steel covered by HVOF coating showed better resistance against NAEC compared to the carbon steel due to higher microhardness and corrosion resistance of their surface-layers. The HVOF coating is hopeful to be applied for NAEC prevention of the components in oil refineries in view of present experimental results.

Review of naphthenic acid corrosion in oilrefining

AbstractNaphthenic acid corrosion is a major concern for the oil refinery business. While much is now known about the phenomenon, it is still not completely understood because of the complex influences on corrosion of the type of acid and other constituents in the crude oil and the effects of both temperature and fluid flow. A review of this form of corrosion has been undertaken with respect to the role of crude oil composition, temperature, fluid velocity, physical state (vapour or liquid), pressure, and materials of construction. Simple measures of corrosivity based on the total acid or neutralisation number are insufficient. The sulphur content of the crude is important but the extent to which the various sulphur containing compounds act as inhibitors or corrodents is not understood. There is little knowledge also of the nature of films formed on the steel surfaces under operating conditions and the role of natural inhibitors that may be present in crudes requires more attention.

Telencephalin induces spreading of microglia

The synergy effect of naphthenic acid corrosion and sulfur corrosion at high temperature in crude oil distillation unit was studied using Q235 carbon-manganese steel and 316 stainless steel. The corrosion of Q235 and 316 in corrosion media containing sulfur and/or naphthenic acid at 280 °C was investigated by weight loss, scanning electron microscope (SEM), EDS and X-ray diffractometer (XRD) analysis. The results showed that in corrosion media containing only sulfur, the corrosion rate of Q235 and 316 first increased and then decreased with the increase of sulfur content. In corrosion media containing naphthenic acid and sulfur, with the variations of acid value or sulfur content, the synergy effect of naphthenic acid corrosion and sulfur corrosion has a great influence on the corrosion rate of Q235 and 316. It was indicated that the sulfur accelerated naphthenic acid corrosion below a certain sulfur content but prevented naphthenic acid corrosion above that. The corrosion products on two steels after exposure to corrosion media were investigated. The stable Cr5S8 phases detected in the corrosion products film of 316 were considered as the reason why 316 has greater corrosion resistance to that of Q235.

Naphthenic Acid Corrosion in Petroleum Refineries. A Review

The problem of naphthenic acid corrosion is specific to certain crudes from India, Romania, Russia, Texas, Venezuela, Congo, Nigeria, etc. The nature of corrosion due to naphthenic acids is in the form of sharp-edged streamlined grooves. Detailed laboratory studies and some field data indicate that naphthenic acid corrosion increases beyond a specific neutralization number of crude, when the process temperature is between 220 and 400°C and when fluid velocities are high. The different factors responsible for naphthenic corrosion as well as the ways of fighting it are reviewed. Among them are predistillation, the blending of crudes, neutralization, the selection of construction materials and especially the mastery of fluid flow.

Naphthenic Acid Corrosion —An Old Enemy Of the Petroleum Industry

Abstract The term “naphthenic acids” is a collective name for organic acids present in various crudes. It has been proved that while minor quantities of other organic acids are included, the main acids from naphthenic base crudes are saturated ring structures containing acid groups. The circumstances under which naphthenic acid corrosion occurs are analogous to those of sulfur corrosion. A practical differentiation between naphthenic acid and sulfur corrosion is possible on the basis of different corrosion phenomena. It would appear that the rate of naphthenic acid corrosion is dependent on the concentration of the naphthenic acids in the oil, operating temperature, fluid velocity and activity of the naphthenic acids. Of these factors fluid velocity seems to be the most important. Unfortunately the critical velocity values below which the corrosion rates become negligible are not yet known. Data are given to show the relationship between temperature and corrosion rates at selected locations in a high vacu...