Pitting corrosion is hazardous for personnel of chemical plants operating with tanks, reactors, and pipelines. Pitting is a pinpointed corrosive damage rapidly penetrating a metal and causing its through-perforation. Chemical and thermal burns and poisoning of personnel are also potential. When designing the equipment, it is required to select materials able to resist pitting corrosion in the operational medium. Quick methods of pitting resistance of material include the comparison of critical potentials determined by potentiodynamic polarization curves. The potential of the studied sample is given a value equal to the corrosion value that is increased at the rate of 0.2–2 mV/s. At the same time, values of current density are registered. The gradual increase of current density is followed by its decrease, and the metal turns to a passive state. With a certain value of pitting formation potential, the current density increases acutely; and pittings are formed on the metal surface. When the potential is decreased, current density within a certain range of values remains relevant to the current density at the pitting formation potential but then decreases to the values relevant to dissolution in a passive state. This occurs at the re-passivation potential.
Earlier, values of potentials of pitting formation and corrosion were compared. Later, it was proved that the evaluation of the pitting resistance of metals based on the comparison was not correct as pittings could also be formed at the potentials lower than the pitting formation potential. The correct evaluation of metal pitting resistance can be obtained based on the comparison of re-passivation and corrosion potentials. Until now, however, the pitting formation potential has been used for the evaluation.
Based on the experimental potentiodynamic polarization curve of stainless steel Х20Н6Г11 and the results of corrosion tests, it has been established that metal corrodes at potentials above the re-passivation potential but lower than the pitting formation potential. When potentials are lower than the re-passivation potential, pittings are not formed.
Corrosion-resistant steels and alloys. Method of accelerated
tests for resistance to pitting corrosion. Available at: https://docs.cntd.ru/document/1200015055 (accessed: February 07, 2024). (In Russ.).
2. Florianovich G.M., Reformatskaya I.I. Metal passivation and re-passivation as a method to prevent corrosive destruction. Zashchita metallov = Protection of metals. 2001. Vol. 37. № 5. pp. 531–536. (In Russ.).
3. Reformatskaya I.I., Podobaev A.N., Trofimova E.V., Ashcheulova I.I. Development of the ideas regarding the role of chromium for the processes of passivation and pitting corrosion of Fe-Cr alloys. Zashchita metallov = Protection of metals. 2004. Vol. 40. № 3. pp. 229–235. (In Russ.).
4. Semiletov A.M., Kudelina A.A., Kuznetsov Yu.I. A superhydrophobic coating and corrosion inhibitors as a combined method for the protection of aluminum alloys in chloride solutions. International Journal of Corrosion and Scale Inhibition. 2023. Vol. 12. № 3. pp. 1321–1335. DOI: 10.17675/2305-6894-2023-12-3-28
5. Luchkin A.Yu., Makarova O.S., Vesely S.S., Goncharova O.A., Andreev N.N. Ethylhexanoic Acid as a chamber inhibitor of zinc-plated steel. International Journal of Corrosion and Scale Inhibition. 2023. Vol. 12. № 2. pp. 586–596.
6. Kasatkin V.E., Kasatkina I.V., Kornienko L.P., Korosteleva I.G., Dorofeeva V.N., Andreev N.N. Catechol as a corrosion inhibitor of steel in an alkaline medium containing chlorides. International Journal of Corrosion and Scale Inhibition. 2023. Vol. 12. № 3. pp. 995–1012. DOI: 10.17675/2305-6894-2023-12-3-12
7. Kasatkin V.E., Dorofeeva V.N., Kasatkina I.V., Korosteleva I.G., Kornienko L.P., Andreev N.N., Gedvillo I.A., Zhmakina A.S. Ascorbic acid as a corrosion inhibitor of steel in chloridecontaining solutions of calcium hydroxide. International Journal of Corrosion and Scale Inhibition. 2022. Vol. 11. № 2. pp. 727–751. DOI: 10.17675/2305-6894-2022-11-2-19
8. Makarova O.S., Luchkin A.Yu., Goncharova O.A., Vesely S.S., Andreev N.N. Chamber protection of galvanized steel. 2. IFKhAN-121, IFKhAN-154 and some mixed inhibitors. International Journal of Corrosion and Scale Inhibition. 2022. Vol. 11. № 2. pp. 762–773. DOI: 10.17675/2305-6894-2022-11-2-21
9. Luchkin A.Yu., Tsvetkova I.V., Kuznetsov I.A., Makarova O.S., Goncharova O.A., Andreev N.N., Vesely S.S. Chamber inhibitors of steel corrosion based on lauric acid, octadecylamine, and their mixtures. International Journal of Corrosion and Scale Inhibition. 2022. Vol.11. № 4. pp. 1734–1748. DOI: 10.17675/2305-6894-2022-11-4-21
10. Tsvetkova I.V., Luchkin A.Yu., Goncharova O.A., Vesely S.S., Andreev N.N. Chamber inhibitors of steel corrosion based on lauric acid. International Journal of Corrosion and Scale Inhibition. 2021. Vol. 10. № 1. pp. 107–119.
11. Kuznetsov D.S., Goncharova O.A., Andreev N.N., Andreeva N.P., Veselyi S.S. IFKhAN-140, a chamber corrosion inhibitor for brass. International Journal of Corrosion and Scale Inhibition. 2020. Vol. 9. № 1. pp. 300–312. DOI: 10.17675/2305-6894-2020-9-1-19
12. Kuznetsov Yu.I., Andreev N.N., Marshakov A.I. Physical and chemical aspects of metal corrosion inhibition. Zhurnal fizicheskoy khimii = Journal of Physical Chemistry. 2020. Vol. 94. № 3. pp. 381–392. (In Russ.).
13. Matvienko M.A., Kovalyuk E.N. Evaluation of pitting corrosion resistance of 12Х18Н9 and 40Х13 steels. Vestnik IrGTU = Vestnik of Irkutsk State Techical University. 2013. № 10 (81). pp. 224–228. (In Russ.).