ABSTRACT

As known, main international standards (ISO 15589-1 and SP0169) protection criteria refer to IR-Free potentials values to be met by applying CP 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, EN 13509 standard proposes different measurement techniques for measuring IR Free potential.

Off potential measurements are usually performed, both on pipeline and by means of coupon, to try catching the best approximation for the IR-free potential value: for this reason, a fully understanding of all the components that contribute to the obtained potential measure is of very great importance for making better assessment.

In this work, an overview of the IR components remaining in Off measurements is shown, in order to give a better understanding of the results obtained while performing a method or another.

Particularly, when performing instant-off measurements on coupon, both the effects of measurement timing and the importance of the design of the stationary reference electrode with coupon used will be shown by means of real field data.

INTRODUCTION

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.

Off potential measurements are usually performed, both on pipeline and by means of coupon, trying to catch the best approximation for the IR-free potential value: for this reason, a fully understanding of all the components that contribute to the obtained potential measure is of a very great importance for making better assessment.

In this paper, an overview of the IR components remaining in Off measurements is shown, in order to give a better understanding of the measure obtained while performing a method or another.

Particularly, when performing instant-off measurements on coupon, both the effects of measurement timing and the design of the stationary reference electrode with coupon used had a significative impact on the measured potentials and remaining IR drop.

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