Materials Performance

DEC 2018

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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28 DECEMBER 2018 W W W.MATERIALSPERFORMANCE.COM 8. C a t h o d i c c u r re n t w a s f u r t h e r increased to I CP = 6.2 mA to bring back I CORR to zero. 9. A third gram of VCI (C) was added to the solution and I CP and I CORR were monitored over 20 h. Similar to the behavior in steps 5 and 7, the inhibitor didn't seem to have any cathodic or anodic polarization effect and resulted in a small "+ve" I CORR value (i.e., ~ +25 µA). 10. CP current was further increased to I CP = 6.3 mA to bring the I CORR value back to zero. 11. At the end of the experiment, the CP system was turned off. Conclusions The results demonstrate that different VCI types interact with CP in substantially different ways. Some have beneficial effects while others can have adverse effects, as follows: 1. VCI types such as VCI (A) have a substantial beneficial and synergis- tic effect with CP, where the inhibi- tor enhances cathodic polarization and reduces CP current require- ment. VCI (A) results show that it caused cathodic polarization by at least –60 mV and reduced the CP current requirement by 48%. 2. VCI types such as VCI (B) cause anodic polarization and may or may not affect CP current require- m ent. V C I (B) re sult s show an anodic polarization of +75 mV and had no substantial effect on the CP current requirement. 3. VCI types such as VCI (C) do not affect polarization potentials while increasing CP current requirement. VCI (C) results showed no effect on cathodic potential but increased the CP current requirement by 10%. In summary, the electrochemical inter- action characteristics of a VCI must be evaluated and verified before it is applied in conjunction with CP to both avoid risk of incompatibility and maximize the benefit of compatibility. Acknowledgments The authors wish to acknowledge the assistance of Andreas Skapoulli at Cortec Middle East and Mohamad Nagi at the American University of Dubai for the test facilities. References 1 C. Pynn, K. Abed, "Compatibility & Interac- tions Between Cathodic Protection and a Vapor Phase Corrosion Inhibitor," CORRO- SION 2017, paper no. 9232 (Houston, TX: NACE International, 2017). 2 S. Al-Sulaiman, H. Sabri, R. Rahim, "Evalua- tion of Cathodic Protection System Criteria on Constructed Tanks Over Bituminous Sand Mix Layer," 14th Middle East Corrosion Con- ference, paper no. 63-CP-10 (Manama, Bah- rain: NACE, 2012). FIGURE 4 Test Results for VCI (C). CATHODIC PROTECTION

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