Issues »  Volume 48, Issue 8

Patterns of the Relationship between the Limit Potentials of the 06KhN28MDT Alloy and Its Indicators in a Gap with a Chloride-Containing Medium Present in the Operation of Heat Exchangers

A. V. Dzhus$^{1}$, O. E. Narivskyi$^{2}$, S. O. Subbotin$^{1}$, G. V. Snizhnyi$^{1}$, T. V. Pulina$^{1}$

$^{1}$National University ‘Zaporizhzhia Polytechnic’, 64 Universytetska Str., UA-69011 Zaporizhzhia, Ukraine
$^{2}$Ukrspetsmash LLC, 7 Haharina Str., Zaporizka Reg., UA-71100 Berdiansk, Ukraine

Received: 13.01.2025; final version - 15.05.2026. Download: PDF

The article develops mathematical models based on regression trees to study the relationship between the repassivation potential (Erep), free corrosion potential (Ecor) of the 06KhN28МDТ alloy in a chloride-containing media, its chemical composition, and structure. As established, Erep shifts in the positive side with an increase in Cr and Cu contents. Specifically, Erep shifts by 192.4 mV within the Cr content range of 23.12–23.68 wt.% and reaches 0.5 V with Cu content up to 2.73 wt.% and Cr content up to 23.125 wt.%. A reduction in the mean austenite grain diameter from 16.5 to 11 μm shifts Erep to the most negative side of 0.287 V. Additionally, when the Cu content exceeds 2.73 wt.% and Cr exceeds 23.125 wt.%, Erep shifts further by 0.265 and 0.23 V, respectively. The hypothesis suggests that Cr forms dense oxide films, while Cu provides anodic protection to grain boundaries. The Ecor potential of the alloy shifts to the most negative side of -0.4557 V as the Cr content decreases from 22.215 down to 21.84 wt.% and Mn decreases from 0.455 down to 0.31 wt.%. With carbon content below 0.053 wt.%, Ecor is of -0.41 V, while the precipitation of Cr and Mo carbides from the austenite solid solution causes only a slight shift in the negative direction. The most positive Ecor value (-0.38 V) is achieved, when the mean austenite grain diameter exceeds 15.5 μm. An increase in Ni content from 27.675 up to 27.730 wt.% shifts Ecor in the negative side by 0.17 V, indicating that Ni has a stronger effect on Ecor compared to Cr and Cu. As found, a decrease in Cr, Mn, and Ni contents in the alloy accelerates general corrosion, but slows down crevice corrosion due to the redistribution of anodic currents. This trend is caused by the redistribution of anodic currents among a large number of dissolution centres of metal atoms in the alloy composition. The constructed mathematical models are recommended for enterprises, which produce plate-like heat exchangers from this alloy to use to select optimal melts in terms of chemical composition and structure, which will ensure maximum resistance of heat exchanger plates to crevice corrosion in the recycled waters of enterprises.

Key words: 06KhN28MDT alloy, crevice corrosion, resistance to crevice corrosion, repassivation potential, free corrosion potential.

URL: https://mfint.imp.kiev.ua/en/abstract/v48/i08/0807.html

DOI: https://doi.org/10.15407/mfint.48.08.0807

PACS: 68.47.Gh, 81.05.Ni, 81.40.-z, 81.65.Kn, 81.65.Lp, 81.65.Rv, 82.45.Bb

Citation: A. V. Dzhus, O. E. Narivskyi, S. O. Subbotin, G. V. Snizhnyi, and T. V. Pulina, Patterns of the Relationship between the Limit Potentials of the 06KhN28MDT Alloy and Its Indicators in a Gap with a Chloride-Containing Medium Present in the Operation of Heat Exchangers, Metallofiz. Noveishie Tekhnol., 48, No. 8: 807–826 (2026)

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