Evaluation of corrosion behaviour of organic coatings with electrochemical noise and electrochemical impedance spectroscopy

Abstract

Electrochemical noise (EN) and electrochemical impedance spectroscopy (EIS) measurements were used to evaluate protective properties and corrosion behaviour of two different organic coating systems. The coatings of commercial grade (zinc rich ethyl silicate) were applied to steel substrates and immersed for up to 3 months in 0 . 5M NaCl at 25uC. An analysis of the EN data was performed during this time, including the measurements of the mean potential E mean , the mean current I mean and the noise resistance R n . The time series noise patterns were transformed into frequency domain by fast Fourier transformation. The power spectral densities (PSDs) of the potential and of the current and roll off slope coatings were then compared with each other. These coated plates were assessed by EIS. Electrolytic penetration through the coating, changes in the dynamic characteristics of the conduction and resistance of the coating film of the protected system as a function of time. Equivalent circuits were used to interpret the physical and electrochemical properties. The mechanism and kinetics of the electrochemical systems were assessed by measuring the fluctuations in capacitance and percentage of water uptake. The coatings were evaluated in salt spray and humidity tests according to ASTM B117 and D2247.

Corrosion protection by acrylamide treatment for magnesium alloy metal matrix composite (MMC) reinforced with titanium boride

“…The corrosion current density is observed to decrease with increasing treatment time. 4. As the treatment time increases, the polarisation resistance and the charge transfer resistance also increase.…”

“…Mahjani et al have evaluated the corrosion behaviour of organic coatings with electrochemical noise and electrochemical impedance spectroscopy. 4 Electrolytic penetration through the coating, changes in the characteristics of resistance of the coating and extent of protection were a function of time. Itagaki et al have studied the organic film degradation by impedance measurements.…”

The Application of Electrochemical Noise for the Study of Metal Corrosion and Organic Anticorrosion Coatings: A Review

“…The change of average potential was not as significant as the average current (Figure 18a). After being immersed in NaCl solution for 3 months, the slope of the current noise PSD spectrum changed slightly (Figure 18b), while that of potential noise varied significantly (Figure 18c) [81] …”

“…After being immersed in 0:5 mol � L À 1 NaCl solution for 3 months, the slope of the current noise PSD spectrum changed slightly (Figure 18b), while that of potential noise varied significantly (Figure 18c). [81] Mills and Mabbutt studied electrochemical noise of defective solvent-borne and waterborne coatings in 0.4 % NaCl solution and 0.35 % (NH 4 ) 2 SO 4 + 0.5 % NaCl solution. [82] The experiment provided the quantitative index to evaluate the coatings through t noise resistance.…”

The EIS‐based Kohonen neural network for high strength steel coating degradation assessment

“…Electrochemical impedance spectroscopy (EIS) is considered as a very powerful technique for evaluating the protective properties of polymer coatings and their degradation during exposure to corrosive environments . The experimental EIS data can be analyzed by appropriate models (eg, equivalent circuits [EC]), and the fitting parameters can be used to reflect coating properties as well as the corrosion reaction at the metal/coating interface, such quantities as coating capacitance, coating resistance, and double layer capacitance.…”