An analytical approach that can discriminate between various forms of microscopic corrosion initiation has been employed in natural gas gathering and storage facilities. Information provided by the analysis of electron microscope coupons has led toward the better understanding and diagnosis of the initial stages of internal corrosion in natural gas gathering and storage facilities.
The corrosivity of four mercaptans and selected crude oil fractions were measured in lab tests. Conclusion: Mercaptan corrosion can contribute significantly to the total sulfur related corrosion in the temperature range 235–300°C, which agrees with observations of elevated temperature corrosion in refinery distillation equipment.
As known, ISO 15589-1 and SP0169 protection criteria refers to IR-Free potentials values to be met by applying cathodic protection to limit corrosion rate and, at the same time, to avoid overprotection: in this respect, according to the type of currents influencing the metallic structure, European standard EN 13509 proposes different measurement techniques for measuring IR Free potential.
Revised in 2020! Cathodic protection (CP) coupons have been used since the 1930s by pioneers of the corrosion control industry, both in North America and in Europe. They have been shown to be a practical tool for determining the level of polarization of a structure and to confirm the IR drop in a potential measurement.
The purpose of this standard is to provide a method for evaluating the effectiveness of a CP system using coupons. It is intended for use by people who design and maintain CP systems for buried or submerged pipelines, underground storage tanks (USTs), on-grade storage tank bottoms, reinforcing steel in concrete, water storage tanks, and various other structures in buried or aqueous environments.
The body of the standard primarily addresses applications for coupons attached to buried pipelines. Appendixes cover the use of coupons for other applications, including USTs, aboveground storage tanks, internal surfaces of water tanks, and reinforced concrete structures.
This revision adds new appendixes on the use of coupons on cased pipelines and the use of coupons to measure alternating current interference data.