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Corrosion and Corrosion Products in a Sour Environment from 80°C to 200°C

Corrosion rate of mild steel and character of corrosion products in sour environments at temperatures from 20 to 200°C. H2S-H2O water chemistry model was developed. Then, H2S corrosion tests were done at 80, 120, 160 & 200°C - exposure time of 4 days.

Product Number: 51317--9084-SG
ISBN: 9084 2017 CP
Author: Shujun Gao
Publication Date: 2017
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The objective of this work was to determine the corrosion rate of mild steel and characterize the corrosion products in sour environments at temperature ranging from 80°C to 200°C. First a H2S-H2O water chemistry model was developed based on available literature for a closed system at high temperature. Then H2S corrosion tests were conducted at 80°C 120°C 160°C and 200°C with an exposure time of 4 days. Linear polarization resistance (LPR) and weight loss (WL) methods were used to measure the corrosion rates. X-ray diffraction (XRD) and scanning electron microscopy with X-ray microanalysis (SEM/EDS) were employed to characterize the corrosion products and surface morphology. The results show that the initial corrosion rates increased with temperature while the steady-state corrosion rates decreased with temperature. The corrosion product was comprised of two distinct layers. The inner corrosion product was always an iron oxide (probably Fe3O4) layer while mackinawite troilite pyrrhotite and pyrite were identified as the main components of the outer layer at 80°C 120°C 160°C and 200°C respectively. Pourbaix diagrams generated based on the analysis of water chemistry corroborated the experimental characterization of the corrosion products.

Key words: hydrogen sulfide, high temperature corrosion, iron sulfide, iron oxide

The objective of this work was to determine the corrosion rate of mild steel and characterize the corrosion products in sour environments at temperature ranging from 80°C to 200°C. First a H2S-H2O water chemistry model was developed based on available literature for a closed system at high temperature. Then H2S corrosion tests were conducted at 80°C 120°C 160°C and 200°C with an exposure time of 4 days. Linear polarization resistance (LPR) and weight loss (WL) methods were used to measure the corrosion rates. X-ray diffraction (XRD) and scanning electron microscopy with X-ray microanalysis (SEM/EDS) were employed to characterize the corrosion products and surface morphology. The results show that the initial corrosion rates increased with temperature while the steady-state corrosion rates decreased with temperature. The corrosion product was comprised of two distinct layers. The inner corrosion product was always an iron oxide (probably Fe3O4) layer while mackinawite troilite pyrrhotite and pyrite were identified as the main components of the outer layer at 80°C 120°C 160°C and 200°C respectively. Pourbaix diagrams generated based on the analysis of water chemistry corroborated the experimental characterization of the corrosion products.

Key words: hydrogen sulfide, high temperature corrosion, iron sulfide, iron oxide

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