Chromate treatments coating structure

Figure 14.12 reports the electrochemical impedance modulus at 0.01 Hz versus immersion time for Zr02 pre-treatments doped with 2-mercaptobenzothiazole. Chromate conversion coating and bare substrate are also reported in the figure. The impedance modulus measured at 0.01 Hz immediately after immersion in the electrolyte (0 h) is approximately 10 ohm cm for the sample coated with Zr02 containing 2-mercaptobenzothiazole (indicated by number 2 in the figure). This sample is structured with two layers of Zr02 oxide and the inhibitor was deposited directly on the pre-treated surface. The inner oxide layer was obtained with 0.1 M precursor concentration and the outer with 0.6 M, as described in the legend of Fig. 14.7B. The impedance modulus of this sample exhibits a rather rapid decrease over 48 h in the electrolyte. However, the modulus of the sample with Zr02 pre-treatment doped with...

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