The object of research is model samples of electrochemically heterogeneous aluminium alloys with copper cathode inclusions of various sizes.
The purpose of the work is to study the influence of the size of cathode inclusions on aluminum alloy corrosion.
Model aluminum experiments were developed with 3 and 16 round copper cathode inclusions of the same total area. These inclusions occupied 10% of the sample area. The change in the potential of free corrosion of model samples in a corrosive solution was studied, their potential-dynamic polarization characteristics and impedance spectral dependences were taken.
It was found that aluminum-copper samples containing 16 copper inclusions have a negative potential for free corrosion to compare to the samples with three copper inclusions. The last circumstance is explained by the greater total length of the perimeters of copper inclusions and, accordingly, the larger area of the anode sections. In this case the area of cathode regions remains unchanged. The dispersion of cathode inclusions reduces the localization of the anode reaction on the aluminum-copper models but obviously increases their overall corrosion.
Impedance dependences indicate that samples with a less number of copper inclusions have higher charge-transfer and higher corrosion resistance. Reducing the size of cathode inclusions leads to an increase in the area of electrochemical activity and the distribution of general corrosion as a result of an increase in the ratio of the area of the anode and cathode regions. In this case localized corrosion decreases.
Adding an inhibitor of a culture supernatant obtained by microbiological synthesis significantly reduces the corrosion of the model aluminum-copper samples in a solution of 0.1% sodium chloride.
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