ABSTRACT

Impressed current cathodic protection (ICCP) is the most common corrosion control method for protecting metallic structures. Mixed metal oxide (MMO) anodes are one of the commonly used impressed current anodes. Such anodes have been widely utilized in the industry due to their good electrocatalytic activity, low consumption rate, long service life, light weight, availability in various shapes, and high ratio of performance to cost. To assess the various MMO ribbon anodes performance in terms of their service life, an electrochemical acceleration life testing (EALT) with relatively high current densities has been conducted. The anode's ability to perform at a higher current density than the application's design requirements was measured, and anodes' performance ranked based on time-to-failure using the EALT. The requested design criteria for the ribbon anodes is current output of 42 mA/m with typical lifetime of 50 years. The tests were conducted in accordance to NACE-TM-0108 on different MMO ribbon anodes, and compared. The EALT results showed that anode Product-A and Product-B did not meet the design specification criteria and failed at application designed current density. Whilst the anodes Product-C and Product-D showed better performance, and met the criteria.

INTRODUCTION

Eliminating and mitigating corrosion is one of the major objectives that oil-and-gas industries are adopting to enhance and optimize the life of their assets. It is achieved by applying scientifically proven concepts that allows industries to with stand corrosion impacts, such as: cathodic protection. It is an electrochemical technique that controls a corrosion cycle by shifting the reaction and electrical potential of the metal surface, which requires protection, from anodic oxidized region to cathodic reduced region.

There are two approaches to implement this theory. One of which is known as Galvanic Anode or Sacrificial Anode for Cathodic Protection System. It is about introducing metals with lower electrical potential than the metallic structures that requires protection. The galvanic anodes, like: Aluminum, Magnesium or Zinc, are placed adjacent to the metallic structures, and connected in the corrosion cycle to be corroded and consumed whilst the remaining areas of the system are rather surviving corrosion attacks. Although this approach requires low maintenance and initial cost, it has limited current capacity that makes it an ineffective option for high-resistivity environments.

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