Experimental Study On On-site Detection Technology Of Organic Coating Quality

Transmission and transformation equipment will be corroded by various environments during the service process,leading to various accidents and seriously threatening the safety of power supply.Anti-corrosion coating is one of the main techniques to prevent corrosion of power transmission and transformation equipment.According to the literature reviewed,the paper will study the existing detection techniques from the appearance,adhesion,thickness,porosity,hardness and other indicators of the paint film,such as the cross-hatch method to measure the adhesion,the pencil method or the Vickers hardness tester.Microscopic observation of thickness and porosity,in order to obtain efficient on-site inspection technology for organic coating quality.According to the environment and conditions of the coating site,a capacitive sensor suitable for on-site electrochemical detection is designed firstly,which is used to test the Electrochemical Impedance Spectrum(EIS)parameters and Mott-Schottky curves of the metal/otganic coating systems.By analyzing and calculating and fitting the data,the parameters of the electrochemical elements of the system equivalent circuit are obtained.From these component parameters,the general performance indicators of the coating are determined.So the requirements of on-site non-destructive testing of coating quality could be met.Based on the capacitance sensor designed above,an experiment was conducted to investigate the influence of the coating thickness on the adhesion of the coating and an experiment to investigate the influence of the quality of pretreatment of the base metal surface on the adhesion.The experimental results show that,under the same conditions,the larger the thickness of the coating,the better the adhesion between the coating and the metal interface.When the thickness increases to a certain value,the influence of the thickness on the adhesion is minimized.The value of the coating used in this experiment is in the range of 120 ～ 170 μm,and the thickness of the coating continues to increase with little change in adhesion;For the pretreatment of the base metal surface,the metal surface is kept dry and clean,and has a certain roughness,which can maximize the interface adhesion and optimize coating corrosion resistance.In this way,after the adhesion of the field coating is measured by the designed capacitive sensor,the interface adhesion can be inferred based on the measured electrochemical parameters,so as to judge the coating quality without damaging the coating.In the investigation experiment of introducing the porosity index into the evaluation of the coating quality index,also by analyzing the electrochemical behavior of metal/coating systems,under different porosity,the larger the amount of charge absorbed by the coating,that is,the resistance decreases,and the system is more susceptible to electrochemical corrosion;in a certain immersion time,the larger the porosity,the faster the coating’s adsorption charge,and the more vulnerable the system is to corrosion.