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Electrochemical tests are utilized for the monitoring and/or controlling of the corrosion current and potential of a material in a corrosive environment to acquire information on:
• Rate of corrosion.
• Susceptibility to localized corrosion.
• Potential for galvanic corrosion.
• Characterization of anodic and cathodic reactions.
These tests typically give more information than common corrosion coupon tests by virtue of the fact that the potential on the specimen can be controlled thereby accelerating or retarding electrochemical reactions related to corrosion on the surface. Electrochemical test techniques include open circuit potential (OCP), potentiodynamic polarization, cyclic polarization, electrochemical impedance spectroscopy, Tafel analysis, galvanodynamic polarization etc. These tests are useful in the study of corrosion of alloys, active/passive behavior, inhibition and stress corrosion cracking.
The measurement of the corrosion potential is a relatively simple concept, with the underlying principle widely used in industry for monitoring corrosion. Changes in corrosion potential can also give an indication of active/passive behavior in stainless steel. When viewed in the context of Pourbaix diagrams, the corrosion potential can additionally give a fundamental indication of the thermodynamic corrosion risk.
Typical corrosion potential plots expected of a good austenitic stainless steel clad, designed and developed to enhance corrosion performance of 1018 steel substrate are presented here as examples.