Specific Features of the Contact Corrosion of Aluminum and Copper in NaCl Solutions

Abstract

It is shown that the corrosion rates of aluminum and copper specimens in a 3% NaCl solution are 1.5–1.7 times higher than in a 0.1% NaCl solution. It is also discovered that the corrosion rate of copper in contact with aluminum placed in 3% NaCl is lower than for its individual specimens and, as the area of aluminum increases, decreases to zero. Thus, in particular, as the area of aluminum specimens (for a constant area of copper specimens) becomes 6.5 times larger, the corrosion rate of aluminum becomes 1.7 times higher. A discrepancy is discovered between the computed values of the rate of contact corrosion of aluminum for high values of the ratio of areas in the aluminum–copper couples and the experimental data. The polarization curves of aluminum in contact with copper placed in 0.1% NaCl are shifted to the region of less negative potentials and the ultimate diffusion and corrosion currents are greater by an order of magnitude than for the individual copper and aluminum specimens. It is established that the KORSOL inhibitor, which satisfactorily inhibits the rates of corrosion of copper and aluminum in tap water, practically fails to protects these metals, including the case of their contact, in 0.1% NaCl, whereas the TIS-4 inhibitor protects the metal by ~ 50–60%.