Materials Performance Supplements

CORTEC 2019

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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uation of samples in triplicate provided much more consistent results. The pres- ence of corrosion inhibitor at the lowest concentrations of 500 ppm showed a signif- icant effect on the corrosion rate, eliminat- ing corrosion on all but one sample. The mass loss of the cleaning procedure was determined to be ~3 mg. The mass loss is the measured mass loss after testing, minus this 3-mg value. Due to rounding, some mass loss values after this correc- tion would be listed as "–1 mg," typically indicating a mass gain. These values are reported as 0 mg in Table 5. Inhibitor concentrations of 800 ppm or greater provided excellent corrosion protection, resulting in a corrosion rate of 0 mpy, corresponding to a corrosion rate reduction of 100%. One sample with inhib- itor concentration of 500 ppm did show some corrosion over the course of testing, corresponding to a corrosion rate of 126.9 mpy, or a corrosion rate reduction of 91.1% (calculated with Equation [2] using the average corrosion rate of control Samples No. 1, 2, and 3). Electrochemical Corrosion Testing EIS testing was performed on the cor- rosion inhibitor of interest at various con- centrations. The test solution utilized a 300-ppm concentration of NaCl in DI water to increase the conductivity and corrosiv- ity of the system. The results of this test- ing show a marked increase in the polar- ization resistance to 1.396 kΩ with just the addition of 100 ppm inhibitor and an even higher resistance when the inhibitor is dosed according to the concentrations tested above. This data is represented in Table 6 and Figure 2. TABLE 6 EIS Testing Results Inhibitor (ppm) OCP (mV) R P (kΩ) Inhibitor Effi ciency (%) 0 –451.0 0.794 0.0 100 –428.0 1.396 43.1 500 –379.4 12.25 93.5 2,000 –376.7 25.64 96.9 5,000 –231.8 43.24 98.2 Conclusions Extraction testing, based on the man- ufacturer's various recommended appli- cations of the VCI oil additive, shows that corrosion inhibitor partitioning results in a concentration of roughly 800 to 1,350 ppm in the aqueous phase, depending on the application method of the VCI oil addi- tive. These results provide a benchmark for corrosion testing, to test the partitioned corrosion inhibitor for its protection capa- bilities in a controlled setting. Initial imm ersion corrosion t esting provided promising results, showing >75% corrosion rate reduction at even the lowest concentration of inhibitor. When reevalua- tion was performed in triplicate, even bet- ter results were seen, showing a complete reduction in corrosion rate in all but one case. It is likely that initial factors such as cleanliness of metal surfaces or the pres- ence of other materials or contaminates can inf luence the corrosion rate. In the context of the real-world application being evaluated, metal surfaces may not be com- pletely clean, and contaminates may be carried into the system by the water as it ingresses. While all these factors may affect the corrosion protection provided by the corrosion inhibitor that partitions from the oil phase to the intruding aqueous phase, it is shown that corrosion inhibitor that naturally partitions into the aqueous phase from the treated oil phase may pro- vide corrosion protection in that system. Results from EIS reinforced the results obtained via immersion testing. Concentra- tions of inhibitor that were much lower than what would be expected in a layup scenario returned polarization resistance values that were notably higher than the non-treated solution. It should also be noted that the chloride concentration utilized in the EIS testing performed would only be seen in very contaminated systems in actual appli- cation. The significant levels of corrosion inhibition observed in such a contaminated system effectively demonstrate the poten- tial protection that can be realized by the passive partitioning of inhibitor from the oil phase into the aqueous phase. FIGURE 2 Inhibitor effi ciency compared to the concentration of corrosion inhibitor from EIS testing. VOLATILE CORROSION INHIBITORS 22 JUNE 2019 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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