Protection of stainless steel in sulfuric acid solution containing hydrogen sulfide by inhibitors

• Ya.G. Avdeev¹, L.V. Frolova², D.S. Kuznetsov², M.V. Tyurina¹ and M.A. Chekulaev¹

¹ K.E. Tsiolkovsky Kaluga state university, Stepana Razina str., 26, Kaluga, 248023 Russian Federation
² A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119071 Russian Federation

Abstract: The corrosion of chromium-nickel steel 1Kh18N9T in 2 М H2SO4 at t = 20–100°C was studied using the mass loss method. In addition, steel hydrogenation in the corrosive medium was measured by the vacuum extraction method. IFKhAN-92 (a 1,2,4-triazole derivative) and its combination with KI were studied as corrosion inhibitors. It was shown that 1Kh18N9T steel has low corrosion resistance in H2SO4 solutions, particularly at temperatures (t) close to 100°C. The steel corrosion rate is k = 1.7–727 g/(m² h) under the conditions studied and increases with increasing t. Steel hydrogenation occurs at t = 40–100°C and is the strongest at 100°C (12 ml/100 g). The presence of 15 mM H2S in the H2SO4 solution slows down steel corrosion (k = 2.8–274 g/(m² h)) but intensifies hydrogen absorption. The highest content of hydrogen absorbed in the metal (36 ml / 100 g) was observed at t = 40°C and 1 h exposure of the specimens. It has been shown that, by themselves, 5 mM IFKhAN-92 or 5 mM KI are not suitable for protection of 1Kh18N9T steel in the specified media, since IFKhAN-92 has low efficiency in H2SO4 solution without H2S, whereas, conversely, KI has low efficiency in H2SO4 solution containing H2S. However, their mixture shows versatile protection in these media. The formulation containing 2.5 mM IFKhAN-92 + 2.5 mM KI that suppresses steel corrosion in H2Scontaining medium up to 100°С and totally prevents hydrogen absorption up to 60°C, inclusive, has been recommended for steel protection in H2SO4, both in the absence and in the presence of H2S. This mixture is particularly efficient in solutions without H2S where it inhibits steel corrosion in the entire t range studied while keeping the content of hydrogen in the metal at metallurgical level.

Keywords: acid corrosion, hydrogen sulfide, corrosion inhibitors, stainless steel, hydrogenation, triazoles

Int. J. Corros. Scale Inhib., 2016, 5, no. 2, 147–158 PDF (301 K)
doi: 10.17675/2305-6894-2016-5-2-4

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