Field-Programmable Gate Array-Based Coating Impedance Detector for Rapid Evaluation of Early Degradation of Protective Coatings

摘要

In this paper, a novel, compact, And field-programmable gate array (FPGA)-based coating impedance detector (CID 2.0) was proposed to rapidly detect the early degradation of coatings. An FPGA-based hardware design with an embedded analog-to-digital converter and digital-to-analog converter was successfully applied to develop CID 2.0. A method for generating high-quality signals for FPGA by using the delta-sigma modulation was used. This method provided higher measurement ranges and accuracies for detecting coating impedance values. The performance of CID 2.0 was compared with that of a conventional potentiostat. For comparison, the impedance value of ideal resistors and commercial coatings was measured using the proposed and conventional methods. The results indicated an optimal correlation between the impedance values measured using CID 2.0 and that measured using conventional potentiostat in the range of 106 - 1010 Ω-cm2. Furthermore, when the continuous monitoring experiments were conducted, CID 2.0 exhibited high sensitivity to detect impedance changes associated with the coating delamination process. The preliminary results suggested that CID 2.0 can be used to observe the changes in the coating impedance values in the critical range to enable workers to determine whether coating maintenance should be scheduled.