EIS Characteristics And Rapid Evaluation Method Of Failure Process Of Conductive Particle Coating In Brine

Coating a coating on a metal surface is one of the simple and economical ways to prevent corrosion of metals. Many methods and tools for studying coating properties have been developed because of the chemical or physical changes that occur during the use of the coating, resulting in a decrease in its protective properties. EIS method is one of the most important tools to study the protective performance of coating in recent years. The EIS study of organic common coating has been systematically studied, but the characteristics of AC impedance spectroscopy with conductive additive Further digging into the study.The zinc oxide coating (zinc powder content of 80 wt% and 90 wt%) was sprayed on the surface of Q235 carbon steel substrate, and three different thicknesses (80μm; 120μm; 160μm) were prepared for each type of coating ).(Magnesium powder added amount of 50 wt%) and magnesium-rich aluminum coating (magnesium powder added amount of 20 wt%, aluminum powder added amount of 30 wt%), magnesium oxide coating on the surface of aluminum alloy spray epoxy coating and each coating was sprayed with three different thicknesses (80μm; 120 μm; 160 μm) to prepare a coating / substrate sample.The electrochemical impedance spectroscopy of the coating in 3.5 wt%NaCl solution was studied by electrochemical impedance spectroscopy (EIS).Fourier transform infrared spectroscopy (FT-IR) was used to analyze the coating functional groups in different immersion stages.The coating sections were observed and analyzed by SEM and EDS for coating corrosion products.In addition, the use of IF phase angle, characteristic frequency method and high frequency phase angle and other rapid evaluation method ofthe coating were evaluated and analyzed and compared. The major obtained results are as follows.(1) Compared with the epoxy varnish coating, the zinc-rich coating resistance of the first decline after the rapid decline and then decline in the early immersion, soaking and epoxy varnish coating similar to the impedance,the impedance has been relatively stable. In the early stage of soaking, the thickness had little effect on the impedance change of the zinc - rich coating,and the change of the coating resistance of three different thicknesses was similar. In the middle of soaking, the thicker the thickness, the higher the impedance value. The porosity of the zinc powder coating is always greater than the porosity of the epoxy varnish coating.(2) Epoxy magnesium-rich coating and epoxy varnish coating with the thickness increases, the impedance increases. Epoxy magnesium-rich coating in the early immersion resistance increased first and then decreased, while the epoxy varnish coating in the immersion process gradually decreased impedance. In the middle of soaking the epoxy varnish coating slowed down and the resistance stabilized and the epoxy magnesium-rich coating decreased slightly after the soaking in the middle of the soaking period and then decreased slightly after a period of time. The porosity of the three magnes of epoxy magnesium-rich coating is close and the variation is similar in the whole soaking process. The porosity of the epoxy-rich magnesium coating is always greater than the porosity of the epoxy varnish coating.(3) At the initial stage of soaking, the coating resistance of the three thick epoxy thick paste (H900) increased first and then decreased, and reached a relatively stable state. During the mid-immersion, the low-frequency impedance (|Z|0.01Hz) tends to be stable and increases from 80 μm, 120 μm, 160μm for each additional 40 μm low impedance to about half an order of magnitude.(4) H900 and epoxy mg and al-rich coating have similar similarity in the initial immersion and soaking period. H900 low-frequency impedance value has been greater than the epoxy mg and al-rich coating low-frequency impedance value. H900 protection than epoxy mg and al-rich coating is more excellent.(5) Epoxy zinc-rich coating (80 wt%) and epoxy zinc-rich coating (90 wt%)can be quickly evaluated using θ0.85 HZ. The 013.7Hz of the epoxy mg-rich coating and the epoxy mg and al-rich coating is consistent with the change of the|Z|0.01Hz, and epoxy mg-rich coating and the epoxy mg and al-rich coating can be quickly evaluated by θ13.7Hz. The characteristic frequency fb is capable of rapid evaluation of the protective properties of epoxy mg-rich coating and the epoxy mg and al-rich coating.(6) The results of SEM show that the metal particles with conductive particles have uniform distribution and effective contact between the metal particles, which can play the role of cathodic protection and conduction. The results of the infrared analysis show that the protective properties of the coating are not deteriorated due to the aging of the coating.