Electrochemical-Impedance-Spectroscopy (EIS) Study of Corrosion of Steels 12CrMoV and SS304 Beneath a Molten ZnCl2–KCl Film at 400 °C in Air

Abstract

The corrosion resistance of 12CrMoV and SS304 steels in contact with a molten mixture of (55-45) mol.% ZnCl 2 -KCl, similar to that found in wasteincineration plants, has been examined in air at 400°C by the electrochemicalimpedance-spectroscopy (EIS) technique. The initial Nyquist plots of 12CrMoV showed a semicircle at high frequency and a line at low frequency indicating a diffusion-controlled reaction. At a later stage, the Nyquist plots are composed of a small semi-circle at high frequency, a line at medium frequency and a large semicircle at low frequency, similar to that shown by SS304 during the whole experimental test. The larger impedance of SS304 as compared to 12CrMoV may be attributed to the presence of Ni and to the higher Cr content of SS304. Equivalent circuits representing the features of the corrosion of 12CrMoV and SS304 are proposed to fit the corresponding impedance spectra, and the electrochemical parameters in the equivalent circuits are calculated.

WC-Co and WC-Co-Cr Coatings for the Protection of API Pipeline Steel from Corrosion in 4% NaCl Solution

“…The EIS technique provides necessary kinetic parameters for the corrosion and corrosion protection of metallic materials in corrosive media [19][20][21][22][23]. Typical Nyquist plots measured for (1) PS, (2) PSC1, and (3) PSC2 after the immersion in 4% NaCl solution for 0.1 h are shown in Figure 1.…”

Effect of Corrosive Medium on the Corrosion Resistance of FeCrMoCB Amorphous Alloy Coating

“…This result shows that corrosion resistance of coating in HCl is better than that in NaOH solution, which is same with study of potentiodynamic polarization. The larger impedance value of coating may be attributed to the presence of the higher Cr content of coating in HCl solution [14]. The alloy containing Cr and Mo is not susceptible to localized corrosion in the Clenvironment and the passive film is generally believed to repair itself [15].…”