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ArticleName Effect of the phase composition of AK12M2 and AK12pch silumins on the corrosion and electrochemical behaviour in weakly alkaline aqueous solution. Part 2. Electrochemical and corrosion testing of silumins under various external conditions in weakly alkaline aqueous solution
DOI 10.17580/tsm.2024.02.05
ArticleAuthor Rakoch A. G., Lobach A. A., Monakhova E. P., Catenda D. P.
ArticleAuthorData

National University of Science and Technology MISIS, Moscow, Russia

A. G. Rakoch, Professor at the Department of Steel Metallurgy, New Production Technologies and Metal Protection, Doctor of Chemical Sciences, Professor, e-mail: rakoch@mail.ru

D. P. Catenda, Postgraduate Student at the Department of Steel Metallurgy, New Production Technologies and Metal Protection


RIFAR JSC, Gai, Russia

A. A. Lobach, Innovation Director, Candidate of Technical Sciences

 

Tsentr Sertifikatsii LLC, Moscow, Russia
E. P. Monakhova, Principal Specialist in Corrosion Protection,Candidate of Technical Sciences, e-mail: evmo444@ya.ru

Abstract

This paper examines and compares the electrochemical and corrosion behaviour of silumins AK12M2 and AK12pch. It was found that despite a greater number of intermetallic compounds in the AK12M2 alloy than in the AK12pch alloy, the rate of their corrosion in a weakly alkaline (pH 8.3) aqueous solution in contact with air at a temperature of 90 оC is almost the same. The latter is due to diffusion control of the cathodic process, which is accompanied by oxygen depolarization. At the same time, at room temperature and with all the other conditions being the same, the corrosion rate of the AK12M2 alloy is higher than that of the AK12pch alloy, which is caused by a higher concentration of intermetallic compounds (cathodes) and a low rate of oxygen diffusion to the cathode areas compared with that at 90 оC. Under anodic polarization, the working electrodes are practically not polarizable, and the corrosion process is accompanied by simultaneous transition of both trivalent and monovalent aluminium cations into the solution. With almost no polarization of anodic processes, this makes the free corrosion potentials independent from changes in the electrolyte temperature. It was established that after deoxygenation of this solution to 0.05 mg/l at room temperature and at 90 оC, the silumins have high corrosion resistance. In this case, the corrosion process is mainly accompanied by hydrogen depolarization as the result of a shift in the free corrosion potential of silumins to negative values. The high corrosion resistance of the AK12M2 and AK12pch alloys in a deoxygenated, weakly alkaline aqueous solution is due to their being in a passive state. Consequently, under these conditions, radiators made of the AK12M2 alloy by injection molding, despite the large number of intermetallic compounds in them, will have a long and trouble-free service life in heating systems.

keywords AK12M2 and AK12pch silumins, intermetallic compounds, corrosion and electrochemical behavior, weakly alkaline solution, concentration of dissolved oxygen, temperature, polarization curves.
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