Abstract
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.
Highlights
In 1956, Derungs^^^ stated that naphthenic acid corrosion was first observed in the 1920's
Lee Craig^^ proposed the use of a corrosive acid number (CAN), determined by calculating the equivalent weight of iron lost by corrosion, and of a naphthenic acid corrosion index (NACI)
The results summarized in figure 1 were produced by performing the Fe powder test with low-sulfur paraffinic white oil with addition of lowsulfur commercially available naphthenic acid
Summary
In 1956, Derungs^^^ stated that naphthenic acid corrosion was first observed in the 1920's. Lee Craig^^ proposed the use of a corrosive acid number (CAN), determined by calculating the equivalent weight of iron lost by corrosion, and of a naphthenic acid corrosion index (NACI). The use of autoclave tests and of a closed loop circuit for hot oil to provide dynamic testing conditions have been proposed as a mean to assess crude corrosivity This has been the main tool used in a multi-client sponsored research on crude corrosivity prediction initiated in 1993. Notice that measuring corrosion rate by weight lost does not make the necessary discrimination between sulfidation and naphthenic acid corrosion This is important because using Cr-Mo steels or stainless steel type 410 or 12 Cr usually solves high corrosivity problems due to sulfidation. It updates the information regarding the latest stages that have been completed in the development process of this new method
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