Influence addition of calcium on corrosion-electrochemical behavior of alloy AF5S10 in aqueous solutions NaCl

It is known that the annual loss of metals from corrosion is 10-15 % of their annual production volume. One way to reduce corrosion of metals is to develop ways to increase their corrosion resistance. One of the main ways to increase the resistance of alloys to corrosion is the purposeful alloying of elements complexly affecting the basic corrosion-electrochemical characteristics of alloys. The paper presents the results of corrosion-electrochemical study of the effect of calcium additives as a structure modifier on the anodic behavior of the alloy AF5S10 (Al + 5 % Fe + 10 % Si), in an aqueous solution of NaCl. Anodic behavior of the AF5S10 alloy modified with calcium. Investigated potentiostatic method in the potentiodynamic mode at a potential sweep rate of 2 mV/s. The calcium supplements in the AF5S10 alloy were from 0.01 to 1.0 % by weight. The studies were carried out in NaCl medium aqueous solution at a concentration of 0.03 %, 0.3 % and 3 % mas. It is shown that with an increase in the chloride ion concentration in the NaCl aqueous solution, the values of free corrosion and pitting potentials are shifted to the negative region. The potential for free corrosion of alloys from time to time shifts to a positive area. This dependence also occurs with an increase in the concentration of the modifier (calcium) in the alloy AF5S10. At the same time, regardless of the composition of the alloys, an increase in their corrosion rate was noted with increasing concentration of NaCl in the solution. The addition of calcium to the alloy AF5S10 almost doubles its corrosion resistance. It is shown that the alloys corrode by the pitting mechanism and calcium as a modifier of the structure of the alloys promotes a shift in the pitting potentials and repassivation into the region of positive values, which, on the whole, leads to an increase in the resistance of alloys to pitting corrosion, and also to the healing of (reassuring) newly arising pitting foci.