Investigation of Electrochemical Noise Method for Coating Field Assessments
Does the Electrochemical Noise Method (ENM) produce field coatings data that is comparable to that achieved through Electrochemical Impedance Spectroscopy?
Reclamation is in the process of implementing EIS for quantitative data evaluations during recoating contracts and coating maintenance inspections. A respected corrosion equipment company, DCVG, recently released the ProCoMeter, which applies a four-probe ENM measurement through a handheld tool that is half the cost of a potentiostat used for EIS. The four-probe ENM measures current and voltage fluctuations that occur as a result of corrosion reactions beneath the coating. The standard deviation of the voltage data, divided by the statndard deviation of the current data, provides the noise resistance, Rn. Rn is roughly equivalent to the total coating resistance derived from EIS in laboratory testing. An evaluation of the new instrument in a field setting is needed to determine if the ENM technique is a potential alternative to EIS. If so, the equipment would be less expensive and easier to use.
Need and Benefit
Quantitative information on coating performance is needed to inform decision-making in order to keep protective costs
at a minimum. The quantitative data can be applied to acceptance of contractor-applied coatings, i.e. quality control
during contracts, as well as for regular maintenance inspections. A portable setup for this field testing exists; it require
a laptop and are in the $15,000 cost range. A new instrument applies electrochemical noise measurements, which
needs to be evaluated, and is approximately half the cost and hand-held.
The outcome of this work is improved tools for evaluating coatings quantitatively. The potential benefit to Reclamation
and other agencies with steel infrastructure, is the ability to better screen contractor quality at the time of coating
application. In addition, coating maintenance inspections that incorporate quantitative data can better determine when
to recoat or perform spot repairs.
Tens of millions of dollars are spent each year maintaining the protective coatings on Reclamation structures.
Identifying and implementing quantitative evaluation techniques will save money through efficiencies related to
reduced occurrences of accepting poorly applied coatings and premature recoating work.
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