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51318-11030- A study on the Effect of Volatile Corrosion Inhibitors on Impressed Current Cathodic Protection

 There is a growing trend to supplement cathodic protection with Volatile Corrosion Inhibitors (VCI) beneath tank floors. This work is to investigate mutual compatibility and interactions of three different volatile corrosion inhibitors and cathodic protection.

 

Product Number: 51318-11030-SG
Author: Khalil M. Abed / Calvin R. Pynn
Publication Date: 2018
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The physical and electrolytic contact between the bottom plate of an aboveground storage tank and the underlying soil typically varies over the area of a tank bottom plates. External tank bottom plates are exposed to both electrolytic and vapor-phase corrosive environments. Cathodic Protection (CP) requires direct electrolytic contact between the tank floor and the underlying soil to effectively mitigate corrosion; hence it is ineffective in a vapor-phase environment.

There is a growing trend to supplement cathodic protection with Volatile Corrosion Inhibitors (VCI) beneath tank floors to specifically address vapor phase corrosion and enhance overall protection of tank bottom plates against soil-side corrosion. The objective of this experimental work is to expand on the study done by Pynn & Abed1 and investigate mutual compatibility and interactions of three different volatile corrosion inhibitors and cathodic protection when applied jointly on an oxygen concentration corrosion macro-cell setup.

The test results varied significantly between the three volatile corrosion inhibitors. One showed it had cathodic polarization effect and resulted in reduction of CP current requirement by 48%. Another had an anodic polarization effect and resulted in reduction of CP current requirement by 2%. Third had no polarization effect, and resulted in an increase of CP current requirement by 10%.

Key words: tank bottom, AST, volatile corrosion inhibitor, cathodic protection, polarization, absorption, macro-cell, vapor phase, corrosion current, air gaps, chime area, soil-side corrosion

 

The physical and electrolytic contact between the bottom plate of an aboveground storage tank and the underlying soil typically varies over the area of a tank bottom plates. External tank bottom plates are exposed to both electrolytic and vapor-phase corrosive environments. Cathodic Protection (CP) requires direct electrolytic contact between the tank floor and the underlying soil to effectively mitigate corrosion; hence it is ineffective in a vapor-phase environment.

There is a growing trend to supplement cathodic protection with Volatile Corrosion Inhibitors (VCI) beneath tank floors to specifically address vapor phase corrosion and enhance overall protection of tank bottom plates against soil-side corrosion. The objective of this experimental work is to expand on the study done by Pynn & Abed1 and investigate mutual compatibility and interactions of three different volatile corrosion inhibitors and cathodic protection when applied jointly on an oxygen concentration corrosion macro-cell setup.

The test results varied significantly between the three volatile corrosion inhibitors. One showed it had cathodic polarization effect and resulted in reduction of CP current requirement by 48%. Another had an anodic polarization effect and resulted in reduction of CP current requirement by 2%. Third had no polarization effect, and resulted in an increase of CP current requirement by 10%.

Key words: tank bottom, AST, volatile corrosion inhibitor, cathodic protection, polarization, absorption, macro-cell, vapor phase, corrosion current, air gaps, chime area, soil-side corrosion

 

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