Mechanism of Electrochemical Corrosion Of Metals Under Insulating Coatings, I. Kinetics of Deterioration of Insulating Coatings On Metals in Electrolytes

The Electrical Properties of Protective Polymer Coatings as Related to Corrosion of the Substrate

“…While these estimates of water uptake may be valid for the early stages of coating exposure to an aqueous environment and for relatively thick coatings, the estimates have limitations. Indeed, porous penetration of conducting phase (8,9), interfacial impedance (10), and Maxwell-Wagner and/or Debye losses within the polymer and interface may all contribute to the observed electrical response of a polymer/substrate system (Ii). In a theoretical discussion, Shmirev and Egorov (12) consider the coating to be represented by a three-element network which may be experimentally determined by a measurement of the impedance at three different frequencies.…”

“…In a theoretical discussion, Shmirev and Egorov (12) consider the coating to be represented by a three-element network which may be experimentally determined by a measurement of the impedance at three different frequencies. Likewise, Tomashov et al (10) suggest that a frequency dependence of the impedance may i11uminate the nature of coating break-down. Preliminary results in this laboratory suggest that the frequency-dependent response of a coating is related to its corrosion protective properties (8).…”

Electrochemical evaluation of defect growth in primers applied on aluminium alloy 2024T3

“…Samples were then polarised at 2 1,400 mV SCE and an impedance measurement was carried out by applying sinusoidal waves of 10 mV in amplitude in a frequency range between 10 5 and 10 2 1 Hz, with ten measurements in logarithmic sequence per frequency decade. An equivalent circuit (Bonora et al, 1996;Tomashov et al, 1964), of the type shown in Figure 2, was used to fit the experimental impedance data. The impedance value from the sample to the reference electrode can be modelled as a parallel circuit representing the impedance of the sample's surface still covered by a good primer film (upper part of the circuit), and the impedance of the defect(s) (lower part of the circuit).…”

Electrochemical Techniques to Monitor Performance of Polymer Coatings in Corrosion Protection

“…The anodic and cathodic polarization curves of the metal under the paint coating give far more information on the corrosion from an electrochemical point of view (Pourbaix et al, 1965;Draley, 1959; Kargin et al, 1958;Eisenfeld et al, 1964;Tomashov et al, 1964; Eisenfeld et al, 1968;Clay, 1969). In this case the ohmic resistance of the coatings causes difficulties as far as the measurement technique is concerned, and if one leaves this question out of consideration he might come to false conclusions.…”