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.

Issue link: https://mp.epubxp.com/i/832839

Contents of this Issue

Navigation

Page 16 of 23

Compatibility and Interactions Between Cathodic Protection and a Vapor Phase Corrosion Inhibitor TABLE 1. EFFECT OF VCI ON ACTIVE CP Event Observation 1 Both coupons were at –774 mV vs. CSE following the preparatory procedure. 2 A macrocell was created by the aeration to achieve a steady state potential difference of ~40 mV between coupons and an I CORR of ~400 µA. The aeration caused potentials of both coupons to shift electropositive as a result of cathodic depolarization. 3 The application of CP with I CP = 5.5 mA caused the cathode coupon to cathodically polarize toward the potential of the anode coupon, thereby reducing I CORR to 0 µA to effectively mitigate the macrocell. 4 An initial 3 g of VCI(x) was added to the solution while I CP was maintained at 5.5 mA. Both coupons shifted electronegative, indicating they were being cathodically polarized. The cathodic polarization of the cathode coupon exceeded that of the anode coupon, resulting in a "-ve" I CORR value (i.e., ~ –200 µA). 5 I CP was reduced to 3 mA to bring I CORR to 0 µA. 6 Further 3 g of VCI(x) was added to the solution while I CP was maintained at 3.0 mA. As was the case following Event 4, both coupons shifted electronegative, but not to the same magnitude as observed with the initial VCI(x) addition, resulting in a "-ve" I CORR value (i.e., ~ –40 µA). 7 I CP was reduced to 2.45 mA to bring I CORR to 0 µA. 8 Further 3 g of VCI(x) was added to the solution while I CP was maintained at 2.45 mA. As was the case following Event 6, both coupons shifted electronegative, but not to the same magnitude as observed with the initial VCI(x) addition, resulting in a "-ve" I CORR value (i.e., ~–20 µA). 9 At Event 7, I CP was reduced to 2.15 mA to bring I CORR to 0 µA. 10 The CP system was de-energized and the cathode potential shifted electropositive and I CORR increased to ~140 µA. 11 When the aeration was stopped, thereby eliminating the driving source for the macrocell, the potential of the cathode coupon approached that of the anode coupon (i.e., –774 mV vs. CSE), and I CORR decreased to ~30 µA. TABLE 2. EFFECT OF VCI IN THE ABSENCE OF CP Event Observation 1 Both coupons were at –777 V vs. CSE following the preparatory procedure. 2 A macrocell was created by the aeration to achieve a steady state potential difference of ~40 mV between coupons and an I CORR of ~375 µA. The aeration caused potentials of both coupons to shift electropositive as a result of cathodic depolarization. 3 An initial 3 g of VCI(x) was added to the solution. Both coupons shifted electronegative, indicating they were being cathodically polarized, and I CORR decreased to ~275 µA. 4 Further 3 g of VCI(x) was added to the solution. Both coupons shifted electronegative, indicating they were being cathodically polarized, and I CORR decreased to ~205 µA. 5 Further 3 g of VCI(x) was added to the solution. Both coupons shifted electronegative, indicating they were being cathodically polarized, and I CORR decreased to ~180 A. 6 The application of CP with I CP = 2.85 mA caused the cathode coupon to cathodically polarize toward the potential of the anode coupon, thereby reducing I CORR to 0 µA to effectively mitigate the macrocell. 7 The CP system was de-energized, the cathode potential shifted electropositive, and I CORR increased back to ~200 µA. 17 CORTEC SUPPLEMENT TO MP MATERIALS PERFORMANCE JUNE 2017

Articles in this issue

Archives of this issue

view archives of Materials Performance Supplements - CORTEC 2017