Evaluation of Alternating Current-Induced Corrosion on Coupons used for Monitoring Applications

Key words: alternating current corrosion, coupon, monitoring INTRODUCTION Oil and gas transmission pipelines that share the right-of-way corridor with electric transmission lines are susceptible to corrosion induced by alternating current (AC) due to inductive and resistive coupling, even if they ar...

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Bibliographic Details
Published inNACE International Corrosion Conference Proceedings pp. 1 - 15
Main Authors He, Xihua S, Shukla, Pavan K, Bourland, Steve, Krissa, Len, DeWitt, Jerry
Format Conference Proceeding
LanguageEnglish
Published Houston NACE International 01.01.2019
Subjects
Alternating current
Aqueous solutions
Cathodic protection
Corrosion
Corrosion effects
Corrosion prevention
Corrosion products
Gas pipelines
Gas transmission
Laboratories
Lasers
Monitoring
Natural gas
Penetration depth
Perturbation
Petroleum pipelines
Pitting (corrosion)
Profilometers
Transmission lines
Uniform attack (corrosion)
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Summary:Key words: alternating current corrosion, coupon, monitoring INTRODUCTION Oil and gas transmission pipelines that share the right-of-way corridor with electric transmission lines are susceptible to corrosion induced by alternating current (AC) due to inductive and resistive coupling, even if they are under cathodic protection (CP). Industry has generally adopted a 1 cm2 circular disk coupon as the "ideal" test surface area because limited studies suggest that this is the dimension most vulnerable to AC corrosion and would lead to conservative estimates of AC corrosion instances in the field. The technique can quantify the corrosion extent by estimating (via pixel counting) the following parameters: corroded volume and mass, corroded area, fraction of the corroded surface, average penetration, deepest penetration, penetration standard deviation, and cumulative distribution of the penetration depth. [...]applied DC formed white deposits from cathodic reaction. * Except for cylindrical specimens, deeper corrosion is predominantly near the edge of the specimens, as seen from the rust distribution on the coupon and one example of the laser profilometer scan of the 5 cm2 circular coupon in Figure 3(b). * Pitting is more predominant than general corrosion, as shown in one example of the pits of the 1 cm2 circular coupon in Figure 3(a). * There is a dynamic buoyancy perturbation effect on the corrosion product formation, which suggests that there is orientation sensitivity of the coupon when immersed in an aqueous solution.