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Simplified Crude Oil Corrosivity Measurement Technique Using Radioactive Tracer Technology, 03-9442

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Principal Investigators
Douglas C. Eberle
Craig M. Wall
Martin B. Treuhaft

Inclusive Dates:  12/01/03 - 04/01/04

Background - SwRI has previously developed a real-time flow loop crude oil corrosivity measurement technique using internal research funding. The real-time flow loop corrosivity test measures corrosion products that are dissolved or eroded into the oil stream during controlled high shear stress conditions. The technique measures corrosion as a function of time and temperature to a time resolution of 10 minutes. While this capability has very high value as a tool for investigating the dynamic behavior of corrosion during various conditions, the complexity of running and maintaining the flow loop makes this a more costly test.

Approach - The purpose of this internal research project was to develop a lower cost, entry-level crude oil corrosivity screening test that would be used primarily to rank the relative corrosivity of test crude oils. In addition, because corrosion rates are highly dependent on protective film buildup, we felt it would be important to develop a measurement technique with the ability to discriminate between corrosion products that adhere to the coupon surface and those that are carried into the oil.

A stirred autoclave test stand was refurbished, and test coupons were designed and fabricated. These coupons were exposed to a thermal neutron flux from a research reactor to convert a small portion of atoms to radioactive Fe-59 and Mn-54, which were used as tracers. A test method was developed in which a radioactive coupon was placed in the test oil in the autoclave vessel. The vessel was sealed and heated to a set point temperature of 600 °F, while the coupon was rotated at 800 revolutions per minute. The sample was held at temperature for 30 minutes, and then allowed to cool. Once cool enough to handle, the vessel was disassembled. Test oil was collected in a Marinelli beaker and radiometrically analyzed for corrosion products. The radiometric counts were converted to mass of corrosion product based upon calibration curves developed from the irradiation. The coupon itself was placed in a vibratory tumbler with abrasive media for a fixed period of time. Upon completion, the coupon was removed, and the abrasive media was collected in a Marinelli beaker for radiometric analysis. These results were converted to what was termed adhesive corrosion product mass.

Accomplishments - Eight test oils, including two spiked reference oils, were tested in this program. Very good confidence limits on individual measurements were obtained, indicating high sensitivity. The samples also demonstrated very good repeatability. This project met its goals by successfully developing a simple, highly sensitive, rapid corrosivity test with the ability to discriminate between adhesive and soluble corrosion products. This project provided a significant advance in SwRI's capabilities through further extension of the proven radioactive tracer technology (RATT®) method. RATT corrosivity measurement is a unique and powerful capability that provides industry with a new and much needed tool for precision measurement of soluble and insoluble corrosion products. SwRI remains a world leader in the application of radioactive tracers for wear and corrosion measurements.

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