The effect of H2S concentration on the corrosion behavior of carbon steel at 90 °C

doi:10.1016/j.corsci.2010.02.004

Corrosion Science

Volume 52, Issue 6, June 2010, Pages 2050-2058

https://doi.org/10.1016/j.corsci.2010.02.004 Get rights and content

Abstract

The electrochemical behavior of SAE-1020 carbon steel in 0.25 M Na₂SO₄ solution containing different concentrations of H₂S at 90 °C was investigated using the methods of weight loss, electrochemical measurements, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the corrosion rate of carbon steel increased significantly with the increase of H₂S concentration. H₂S accelerated the corrosion rate of SAE-1020 carbon steel by a promoted hydrogen evolution reaction. Severe corrosion cavities were observed on the carbon steel surface in the solutions containing H₂S due to cementites stripped off from the grain boundary. The loose corrosion products formed on the steel surfaces were composed of mackinawite.

Introduction

The evaluation of metallic materials corrosion in oil refinery environments is a very important issue, especially in distillation plants, as this phenomenon is responsible for costly economic and human losses. The most important corrosive agents in primary distillation plants are chlorides and H₂S [1]. It is very useful to know the mechanism of action of different corrosive agents on metallic materials in oil refinery environments. In this regard, the electrochemical behaviors of both iron and steel in solutions with chlorides and H₂S have been investigated through the years by many researchers [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]. In the literature, there are studies of the effect of H₂S concentration on steel [2], iron [3], [4], [5], [6], chromium [7] and nickel [8], the effect of Cl⁻ on steel [9], the effect of Cl⁻ and H₂S on steel weld [10], [11], [12], [13], and the effect of buffered acetic acid solutions with chlorides and H₂S on steel [1], [14]. The results demonstrated that H₂S could accelerate both the anodic iron dissolution and the cathodic hydrogen evolution in most cases [3], [4], [5], [6], but some results showed that H₂S could also inhibit the corrosion of iron under certain special conditions [4], [5]. Though much effort has been put into H₂S or Cl⁻ corrosion, little research have been carried out on the temperature of the condensation system in primary distillation plants, which usually is greater than 70 °C. Therefore, it is of great interest to study carbon steel corrosion process in H₂S–HCl–H₂O system by simulation of oil refinery conditions at a temperature greater than 70 °C.

In the present work, weight loss test, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to investigate the effect of H₂S concentration on the corrosion of SAE-1020 carbon steel at 90 °C.

Section snippets

Experimental setup

Experiments were conducted at atmospheric pressure in a glass cell (Fig. 1). A typical three-electrode setup was used with a saturated calomel electrode (SCE) (GD-II, BRICEM, China) as the reference electrode, a large piece of platinum with a surface area of over 4 cm² as the counter electrode, and a SAE-1020 carbon steel specimen as the working electrode. The temperature of electrolyte solutions was controlled with a bath at 90 ± 1 °C. Residual H₂S was absorbed by gas absorbent.

Material and specimen preparation

The material

Microstructure

The result of the microstructure observation of SAE-1020 carbon steel is shown in Fig. 2. The phase of carbon steel mainly consisted of ferrite (F). A mass of carbide (Fe₃C) deposited in the grain boundary especially in the tri-angle grain boundary was also observed.

Corrosion rates of carbon steel

With respect to the determination of corrosion rate, the most accurate and precise method is probably that of weight loss [15]. The average corrosion rates of carbon steel in the H₂S-containing solutions obtained from weight loss

Conclusion

The corrosion rate of SAE-1020 carbon steel at 90 °C increased with the increase of H₂S concentrations from 58.91 to 408.44 mg L⁻¹. H₂S showed strong acceleration effect on the cathodic hydrogen evolution of carbon steel, causing carbon steel to be seriously corroded. The corrosion products formed on carbon steel surfaces in the solutions containing H₂S at 90 °C were composed of mackinawite, which was loose and did not show any protective property in the solution containing H₂S at 90 °C. Severe

Acknowledgement

The authors acknowledge support of The Academe of Lanzhou Petrochemic Company, CNPC.

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The effect of H2S concentration on the corrosion behavior of carbon steel at 90 °C

Abstract

Introduction

Section snippets

Experimental setup

Material and specimen preparation

Microstructure

Corrosion rates of carbon steel

Conclusion

Acknowledgement

Electrochim. Acta

J. Electroanal. Chem.

Corros. Sci.

Corros. Sci.

Corros. Sci.

Mater. Sci. Eng. A

Mater. Chem. Phys.

Electrochim. Acta

Corros. Sci.

Ultrason. Sonochem.

Electrochim. Acta

Electrochim. Acta

Electrochim. Acta

Corros. Sci.

Electrochim. Acta

Corros. Sci.

Corros. Sci.

The effect of H2S concentration on the corrosion behavior of API 5L X-70 steel

J. Solid State Electrochem.

Theoretical interpretation on impedance spectra for anodic iron dissolution in acidic solutions containing hydrogen sulfide

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Corrosion of iron in acid solutions with hydrogen sulfide

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Aqueous corrosion behavior of weathering steel and carbon steel in acid–chloride environments

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Effect of sulfide ions on the corrosion behavior of mild steel in acetate buffer

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A study of corrosion behavior of copper in acidic solutions containing cetyltrimethylammonium bromide

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