ISO 22426-2020 pdf free.Assessment of the effectiveness ofcathodic protection based on couponmeasurements.
This document specifies requirements for the design，installation，positioning，sizing，use andmaintenance of coupons for the assessment of the effectiveness of cathodic protection (CP) of buriedand immersed metallic structures, such as pipelines, in the case of normal operation as well as AC andDC interference conditions.
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document.For dated references,only the edition cited applies. Forundated references, the latest edition of the referenced document(including any amendments) applies.ISO 15589-1，Petroleum, petrochemical and natural gas industries — Cathodic protection of pipelinesystems —Part 1: On-land pipelines
EN 50162,Protection against corrosion by stray current from direct current systems.
For the purposes of this document, the following terms and definitions apply.
activation polarization:change of an electrode [e.g.structure (3.13) and/or coupon(3.14)] potential due to charge transfer
depolarization:loss of polarization(3.3) of an electrode [e.g.structure(3.13) and/or coupon(3.14)] potential subsequentto current interruption
Note 1 to entry: Loss of concentration polarization (3.4) of an electrode (e.g. structure or coupon) is > 102 s upto seconds, hours or days. Only a small fraction of concentration polarization is usually lost within 0,1 s aftercurrent interruption in most cases. The time constant for build-up and depolarization of activation polarization(3.5)of an electrode is from 10-4 s to 10-3 s.Therefore, usually all activation polarization is lost within 0,1 s aftercurrent interruption.
IR drop:voltage, due to any current,developed in an electrolyte (3.2) such as soil, between the referenceelectrode and the metal of the structure (3.13), in accordance with 0hms Law (U=lxR)
IR-free potentialEIR free:electrode [e.g. coupon (3.14)] to electrolyte(3.2) potential measured without the voltage error causedby the IR drop (3.7) due to the protection current or any other current
instant-off potentialEoff:electrode [e.g.structure(3.13〕 and/or coupon(3.14)] to electrolyte(3.2) potential measured very quickly(typically <0,3 s) after an interruption of all sources of applied cathodic protection current with theaim of approaching an IR-free potential (3.8)
Note 1 to entry: The delay between the current interruption and measurement will affect the measured valueand whether there is a decay of concentration polarization(3.4) and/or activation polarization(3.5).ISO 22426 pdf download.