Materials Performance Supplements

CORTEC 2017

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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VAPOR PHASE CORROSION INHIBITORS Test Procedure Events 1. Test start—steady state coupon potentials following preparatory procedure 2. Aeration started to create stable macrocell with potential difference of -40 mV 3. CP output current energized and adjusted to reduce I CORR to 0 µA 4. 3 g VCI(x) added to solution 5. CP output reduced to maintain I CORR at 0 µA 6. 3 g VCI(x) added to solution 7. CP output reduced to maintain I CORR at 0 µA 8. 3 g VCI(x) added to solution 9. CP output reduced to maintain I CORR at 0 µA 10. CP de-energized 11. Aeration stopped 12. Test end Test Procedure Events 1. Test start—steady state coupon potentials following preparatory procedure 2. Aeration started to create stable macrocell with potential difference of -40 mV between coupons and I CORR of –375 µA 3. 3 g VCI(x) added to solution 4. 3 g VCI(x) added to solution 5. 3 g VCI(x) added to solution 6. CP output current energized and adjusted to reduce I CORR to 0 µA 7. CP de-energized 8. Test end FIGURE 3 Test 1 results—effect of VCI on active CP system. FIGURE 4 Test 2 results—effect of VCI in the absence of CP. rate of 375 µA was reduced by 27% with the first 3 g addition, 45% with further 3 g addition, and 52% with the final 3 g addition. 2. With respect to CP: a. CP can completely mitigate liq- uid-phase macrocell corrosion. b. CP appears to enhance the absorp- tion and effectiveness of the inhibi- tor at the cathodic metal surface. Caveats to Conclusions— Limitations of Testing 1. The test results revealed in this work apply to the specific VCI type and concentra- tions tested and are definitely not indic- ative of all inhibitors. For example, com- pletely different results would be expected for "anodic inhibitor" chemistries. 2. There are many types and chemistries of corrosion inhibitors with varying appli- cation concentrations on the market having specific properties that differ from the VCI tested in this work. Each of these should undergo similar testing as that performed in this work to spe- cifically evaluate their effectiveness and compatibility. 3. It must be emphasized that this work evaluates the effectiveness and compat- ibility in the liquid-phase exposure. It does not in any way reflect the effective- ness of the inhibitor to reduce corrosion in the vapor-phase for which it is primar- ily intended. 4. As inhibitors generally affect the electro- chemical reactions at the metal-electro- lyte interface, and therefore their poten- tials, the presence of any inhibitor in the electrolyte would be expected to affect the potential stability of permanent reference electrodes used for CP per- formance evaluation, and similarly, the potential of any galvanic anodes in the same environment. 5. It is recognized that the time between test stages was limited and therefore not suffi- cient for parameters to reach a true steady state before adjusting variables. These times should be extended in future work. Acknowledgments The authors wish to acknowledge the assistance of Dr. Mohamad Nagi and the American University of Dubai for the test facilities and Andrea Skapoulli of Cortec Middle East. Reference 1. NACE No. 1/SSPC-SP 5/Sa 3, "White Metal Blast Cleaning" (Houston, TX: NACE International). Bibliography Abed, K., P. Panchai, A. Gamdo. "Evaluation of Im- pressed Current Cathodic Protected API 650 Tank Bottoms in the Presence of Vapor Phase Corrosion Inhibitor." CORROSION 2016, paper no. 7600. Houston, TX: NACE International. Al-Sulaiman, S., H. Sabri, R. Rahim. "Evaluation of Cathodic Protection System Criteria on Con- 16 JUNE 2017 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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