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Can an Intermittent Cathodic Protection System Prevent Corrosion of Buried Pipeline?

In this paper, a preliminary study of the effect of intermittent CP has been carried out in order to investigate the effect of a temporary current interruption on the potential monitoring and on the residual corrosion of the metal.

 

Product Number: 51317--9353-SG
ISBN: 9353 2017 CP
Author: Marco Ormellese
Publication Date: 2017
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Usually cathodic protection (CP) is continuously applied to control corrosion of buried pipeline. The effect of cathodic reactions (oxygen reduction and/or hydrogen evolution) taking place on the metal surface is twofold: oxygen consumption and alkalization (pH > 10) at the metal-to-electrolyte interface leading carbon steel to work in passive condition. Aim of the research is to exploit the chemical and electrochemical condition at the metal interface to apply an intermittent CP: during the ON period oxygen is consumed and alkaline pH is established during OFF period the alkalinity produced in the previous phase assure passive condition until neutral condition re-establishes then CP is switched on again.Test has been performed both in normal and overprotection condition varying the duration of the on and off periods (6 h 12 h and 18 h) monitoring weekly the protection potential and the protection current. At the end of the test residual corrosion rate has been evaluated by weight loss measurements.

Key words: Cathodic protection, carbon steel, protection potential, oxygen reduction, overprotection

Usually cathodic protection (CP) is continuously applied to control corrosion of buried pipeline. The effect of cathodic reactions (oxygen reduction and/or hydrogen evolution) taking place on the metal surface is twofold: oxygen consumption and alkalization (pH > 10) at the metal-to-electrolyte interface leading carbon steel to work in passive condition. Aim of the research is to exploit the chemical and electrochemical condition at the metal interface to apply an intermittent CP: during the ON period oxygen is consumed and alkaline pH is established during OFF period the alkalinity produced in the previous phase assure passive condition until neutral condition re-establishes then CP is switched on again.Test has been performed both in normal and overprotection condition varying the duration of the on and off periods (6 h 12 h and 18 h) monitoring weekly the protection potential and the protection current. At the end of the test residual corrosion rate has been evaluated by weight loss measurements.

Key words: Cathodic protection, carbon steel, protection potential, oxygen reduction, overprotection

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