Field Validation of Impedance Spectroscopy Coating Assessments
Can electrochemical impedance spectroscopy (EIS) data be used to improve planning for recoating critical metalwork at Reclamation facilities as well as the effectiveness of coating specifications for rehabilitation activities? TSC coatings specialists developed an EIS field method in 2014 to support traditional observations and qualitative coating evaluations made during facility coating condition assessments. Validation of the method will legitimize conclusions drawn from the data and determine the appropriate implementation of the method. Advancement in this technique would improve prediction of the coating's end of useful life, improving maintenance planning and overall cost of corrosion economics.
Need and Benefit
Most of Reclamation's facilities have critical metalwork protected by coating systems. Timing the coating maintenance is challenging, and the work is expensive. Routine coating condition assessments help to determine the timing and type of coating maintenance activities required, but the traditional inspection techniques are largely qualitative. This research is needed to support the ongoing implementation of a quantitative tool for assisting facility owners with coating maintenance planning and contract adherence.
EIS analysis provides a simple, quantification of the total resistance or corrosion protection provided by the coatings, leaving facility owner's much better-informed. Field EIS measurements may also improve quality control testing during recoating projects. These contracts often exceed $1 Million. EIS testing could save months of effort and millions of dollars if a poor quality coating application is halted at the initial stages of the project. Field condition assessments or coating contract work can include EIS testing for less than $1,000, assuming a trained inspector is already on site.
Corrosion costs are approximately 3% of the nation's gross domestic product. Reclamation's structures are aging, and the cost of corrosion control may increase significantly in future years if we maintain the status quo for coating maintenance planning and specifications. As an example, recoating work performed at Parker Dam was substandard by EIS data interpretation, but the existing quality control techniques failed to identify the poor coating quality. EIS testing could be integrated with existing techniques to determine the substandard product early in the contract and the issue resolved before further recoating.
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