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NACE Publication 35201-2001-SG, Technical Report on the Application and Interpretation of Data from External Coupons Used in the Evaluation of Cathodically Protected Metallic Structures

CP coupons have been used since the 1930s by several of the pioneers of the corrosion-control industry, both in North America and in Europe. Over the last two decades, the use of CP coupons has been rediscovered as a practical method to determine the level of polarization of a buried structure and to confirm the voltage drop in a potential measurement. Acceptance of CP coupon technology is slowly occurring. Research sponsored by the pipeline industry has explored the use of CP coupons and has helped validate the use of this technology.

Product Number: 24213-SG
Publication Date: 2001
$79.00
$79.00
$79.00

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Coupons can be used to determine the level of corrosion protection provided by a cathodic protection (CP) system to a buried structure, such as an operating pipeline. Structure-to-electrolyte potential measurements have long been used as the basis for assessing cathodic protection levels and compliance with CP criteria. It is well known that a voltage (IR) drop exists in the soil or across the coating, and that this IR drop can produce an error in the interpretation of the structure-to-electrolyte potential measurement. This voltage drop can be a function of reference electrode placement, soil resistivity, burial depth of the structure, coating condition, and the amount of CP current applied. 

CP coupons have been used since the 1930s by several of the pioneers of the corrosion-control industry, both in North America and in Europe. Over the last two decades, the use of CP coupons has been rediscovered as a practical method to determine the level of polarization of a buried structure and to confirm the voltage drop in a potential measurement. Acceptance of CP coupon technology is slowly occurring. Research sponsored by the pipeline industry has explored the use of CP coupons and has helped validate the use of this technology. The purpose of this technical committee report is to provide an alternative to the conventional evaluation of the effectiveness of a CP system.

Coupons can be used to determine the level of corrosion protection provided by a cathodic protection (CP) system to a buried structure, such as an operating pipeline. Structure-to-electrolyte potential measurements have long been used as the basis for assessing cathodic protection levels and compliance with CP criteria. It is well known that a voltage (IR) drop exists in the soil or across the coating, and that this IR drop can produce an error in the interpretation of the structure-to-electrolyte potential measurement. This voltage drop can be a function of reference electrode placement, soil resistivity, burial depth of the structure, coating condition, and the amount of CP current applied. 

CP coupons have been used since the 1930s by several of the pioneers of the corrosion-control industry, both in North America and in Europe. Over the last two decades, the use of CP coupons has been rediscovered as a practical method to determine the level of polarization of a buried structure and to confirm the voltage drop in a potential measurement. Acceptance of CP coupon technology is slowly occurring. Research sponsored by the pipeline industry has explored the use of CP coupons and has helped validate the use of this technology. The purpose of this technical committee report is to provide an alternative to the conventional evaluation of the effectiveness of a CP system.

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