varela-electrochemicalmethod-2015.pdf (3.01 MB)
Electrochemical method for studying localized corrosion beneath disbonded coatings under cathodic protection
journal contribution
posted on 2015-01-01, 00:00 authored by Bob Varela, Mike Yongjun TanMike Yongjun Tan, Maria ForsythMaria ForsythThis paper presents a new method for measuring localized corrosion under disbonded coatings by means of an electrochemical sensor, denoted differential aeration sensor (DAS). It measures the distribution of electrochemical currents over an electrode array surface partially covered by a crevice that simulates a disbonded coating. The DAS has been evaluated using immersion tests at open circuit and under cathodic protection (CP) conditions. Under both conditions, anodic as well as cathodic current densities were detected within the crevice. A fundamental understanding for the detection of anodic currents under CP has been explained in terms of basic electrochemistry. Based on the current distribution data provided by the sensor, two different analysis methods have been used to estimate corrosion and its distribution. These methods consisted of a direct application of Faraday's Law to the anodic currents detected by the array, and on a sensor-specific method denoted corrected currents' method. It has been demonstrated that under diffusion controlled conditions this latter method produces a better corrosion estimation than the direct application of Faraday's Law. The corrected currents' method allowed the estimation of corrosion patterns outside the crevice under CP. Good correlation between electrochemical calculations and surface profilometry results has been obtained.
History
Journal
Journal of the electrochemical societyVolume
162Issue
10Pagination
C515 - C527Publisher
Electrochemical SocietyLocation
Pennington, N. J.Publisher DOI
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ISSN
0013-4651eISSN
1945-7111Language
engPublication classification
C Journal article; C1 Refereed article in a scholarly journalCopyright notice
2015, Electrochemical SocietyUsage metrics
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