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

Abstract

The corrosion of chromium-nickel steel 1Kh18N9T in 2 М H 2 SO 4 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 H 2 SO 4 solutions, particularly at temperatures (t) close to 100°C. The steel corrosion rate is k = 1.7-727 g/(m 2 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 H 2 S in the H 2 SO 4 solution slows down steel corrosion (k = 2.8-274 g/(m 2 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 H 2 SO 4 solution without H 2 S, whereas, conversely, KI has low efficiency in H 2 SO 4 solution containing H 2 S. 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 H 2 Scontaining medium up to 100С and totally prevents hydrogen absorption up to 60°C, inclusive, has been recommended for steel protection in H 2 SO 4 , both in the absence and in the presence of H 2 S. This mixture is particularly efficient in solutions without H 2 S where it inhibits steel corrosion in the entire t range studied while keeping the content of hydrogen in the metal at metallurgical level.

High-temperature inhibitors of stainless steel corrosion in sulfuric acid solutions

“…However, the corrosion of steel systematically accelerates with an increase in t and, according to the data of 0.5 h tests, it reaches 0.3 kg/(m 2 ·h) at 80°C, 0.7 kg/(m 2 ·h) at 100°C, and 9.7 kg/(m 2 ·h) at 200°C (Figure 1). The equimolar mixture of IFKhAN-92 and KI that we previously developed [23][24][25] for the protection of stainless steels in sulfuric acid media efficiently protects the metal in 2 M H 2 SO 4 at rather low concentrations (C mix = 5 mM) at t ≤ 140°C, where k ≤ 10 g/(m 2 ·h) ( Table 1). However, a further t increase by 20°C abruptly decreases  3-fold (in 0.5 h tests).…”

“…Our previous studies [23][24][25] on the corrosion behavior of chromium-nickel stainless steels in this medium at t ≤ 100°C allow us to assume that their stability is low under these conditions.…”

“…As the basis for the creation of composite inhibitors, we studied IFKhAN-92, whose mixtures with KI considerably hinder the corrosion of chromium-nickel steels in H 2 SO 4 solutions at t ≤ 100°C [23][24][25] and the corrosion of low-carbon steel at t ≤ 200°C [20][21][22]. It is important to estimate the ability of formulations that we developed for the protection of stainless steels to inhibit the corrosion of low-carbon steels as well.…”

Synthesis, characterization, and evaluation of some acyclic S-nucleosides of pyrazolo[3,4-d]pyrimidine-thiones as corrosion inhibitors for carbon steel in hydrochloric acid

“…decrease and hence the values of IE's increase, indicating the inhibiting effect of these compounds toward the corrosion of carbon steel in 1.0 M HCl solutions. The corrosion inhibition efficiency is given by the following equation [28][29][30][31][32][33]: %IE = 1-(I inh /I uninh ) × 100 (6) where: I uninh and I inh are the corrosion current densities in the absence and presence of inhibitor respectively. …”

Polyoxyethylene stearate of molecular weight 6000 as corrosion inhibitor for mild steel in 2.0 M sulphuric acid

“…The surface coverage () and the inhibition efficiency P(%) of the inhibitor can be calculated from I corr values according to the following equationы (Eq. 1 & 2), assuming that the inhibitor in question has a blocking mechanism of action [36][37][38][39].…”