Materials Performance Supplements

CORTEC 2017

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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VAPOR PHASE CORROSION INHIBITORS Compatibility and Interactions Between Cathodic Protection and a Vapor Phase Corrosion Inhibitor Calvin R. Pynn, AEGIS Technical Systems LLC, Dubai, United Arab Emirates Khalil a bed, Cortec Middle East, Dubai, United Arab Emirates The nature of the physical contact be- tween the bottom plate of an above- ground storage tank and the underly- ing foundation/soil varies considerably over the area of a tank bottom and from tank to tank. This may vary from direct electrolytic contact between the plate and moist underlying soil to void spaces between the plate and the soil due to floor buckling and/or soil settlement. Cathodic protection (CP) is a proven corrosion mitigation technique where the target metal sur- face is in contact with a conductive electrolyte such as moist soil, but it will not be effective in void spaces where there is no electrolyte contact with the tank floor. Consequently, there is increasing application of va- por phase corrosion inhibitor (VCI) in- jection beneath tank bottoms to en- sure corrosion is mitigated in the void spaces. The objective of this work was to evaluate the mutual compatibility and interactions between CP and a VCI where applied together in a liq- uid-phase environment. The work comprised laboratory experiments to quantitatively evaluate the effects of a particular amine carboxylate-based inhibitor and CP, when applied indi- vidually and jointly on an oxygen con- centration corrosion macrocell in a salt water solution. The results indi- cate a beneficial synergistic effect be- tween the particular inhibitor tested and CP, where the inhibitor enhances cathodic polarization to reduce CP current requirement, and CP reduc- tion reaction appears to enhance the absorption and effectiveness of the inhibitor at the cathodic metal sur- face. The nature of the physical contact between the bottom plate of an above-ground storage tank and the underlying foundation/soil varies considerably over the area of a tank bottom and from tank to tank. This may vary from direct electrolytic contact between the plate and moist underlying soil to void spaces between the plate and the soil due to floor buckling and/or soil settlement. Cathodic protection (CP) is an effective corrosion mitigation technique where there is an electrolytic contact between the tank bottom surface and the underlying soil (i.e., liquid-phase environment), but it cannot provide protection in the absence of an elec- trolyte, as is the case where there are gaps or voids between the tank bottom and soil, or where there is intermittent moisture in the soil contacting the tank bottom surface (i.e., vapor-phase environment). Increasingly, vapor phase corrosion inhibitors (VCIs) are being injected beneath tank bottoms to mitigate the vapor-phase corrosion aspect. There are many types and chemistries of corrosion inhibitors that affect the electrochemical reactions at the metal-electrolyte interface. Each of these has specific properties that may or may not be compatible with CP or other corrosion prevention measures. The objective of this work was to eval- uate the mutual compatibility and interac- tions between CP protection and a particu- FIGURE 1 Test setup—schematic. FIGURE 2 Test setup—physical arrangement. 14 JUNE 2017 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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