Protective efficiency of the expired drug Drotaverine against hydrogen sulfide corrosion of St3 steel

• L.E. Tsygankova, V.A. Kur’yato, R.S. Alekseev, D.O. Evtyukhin and V.A. Zhivoderova

Derzhavin State University, ul. Internatsionalnaya, 33, 392000 Tambov, Russia

Abstract: In the last decade, there has been active research of expired drugs as inhibitors of metal corrosion in various aggressive environments. In this work, the inhibitory effect of the expired drug Drotaverine against corrosion of St3 carbon steel in model stratum waters of the oil and gas fields, NACE and M1, saturated with 400 mg/L H₂S, was studied. The concentration of the drug varied within the range of 20–80 mg/L. The protective effect of Drotaverine (80 mg/L) amounts to 79% and 76%, according to 24-hour gravimetric tests, in the NACE and M1 environments, respectively. The protective effect approaches 90% when urotropine (1 mM) and KCNS (0.5 mM) are added to the solutions along with Drotaverine (80 mg/L). The mutual influence of the components of the inhibitory mixtures in the environments studied was assessed. Analysis of polarization curves in the environments under study showed that Drotaverine slows down both partial electrode reactions in the NACE+H₂S medium and the cathodic process in M1+H₂S. In the joint presence of the drug and KCNS, primarily the cathodic process is inhibited, with no effect on the anodic one in both environments. The same pattern is characteristic for the joint presence of Drotaverine and Urotropine. Drotaverine reduces the rate of hydrogen diffusion into the metal in the M1+H₂S media and slows down the growth of sulfate-reducing bacteria in Postgate’s “B” medium.

Keywords: expired drug, Drotaverine, carbon steel, hydrogen sulfide, corrosion, inhibition, protective efficiency, hydrogen diffusion, SRB

Int. J. Corros. Scale Inhib., 2026, 15, no. 1, 508-522
doi: 10.17675/2305-6894-2026-15-1-26

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