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Mechanical Properties of a Mackinawite Corrosion Product Layer

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To develop a holistic understanding of corrosion mechanisms in upstream oil and gas pipelines mechanical properties of the corrosion product layers as well as corrosion mechanisms need to be studied for better prediction of general and localized corrosion. Various ongoing research has focused on the topic of sour corrosion mechanisms while minimal attention has been paid to ascertaining the mechanical properties of the iron sulfide layers developed in these environments. The effects of fluid flow (i.e. erosion/corrosion wall shear stress) as well as the impact of different operations (i.e. wellbore cleaning wireline tools) on the internal pipeline wall may lead to a partial removal of corrosion product layers. This is an important topic since the mechanical damage of protective iron sulfide layers may lead to localized corrosion. To investigate the magnitude of stress required to damage iron sulfide layers up to the point of exposing the substrate well-defined iron sulfide layers were developed in a 4-liter glass cell and the mechanical properties of the layers such as hardness and adhesive strength were investigated using a mechanical tester. To develop the iron sulfide layer UNSG10180 carbon steel specimens were exposed to a 1 wt.% NaCl solution at pH of 6.0 well purged with a 10 mol.% H2S/N2 mixture. Fes layers were developed at two solution temperatures 30⁰C and 80⁰C and the hardness and interfacial shear strength of the layers formed after 1 day and 3 days were investigated. The morphological characteristics of the FeS layers under investigation were examined by conducting an SEM and cross-sectional analysis. XRD analysis confirmed mackinawite as the phase of the iron sulfide layer. While the interfacial shear strength of this FeS layer was found to be 5 magnitudes higher than the maximum flow related shear stress the integrity may be compromised if these layers are subjected to other mechanical impacts that may occur during production.

Product Number: 51319-13441-SG

Author: Ezechukwu Anyanwu

Publication Date: 2019

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Fe3O4, FeCO3 or FeS - Which Corrosion Product Will Prevail at High Temperature in CO2/H2S Environments?

Product Number: 51320-14413-SG

Author: Shujun Gao, Bruce Brown, David Young, Srdjan Nesic, Marc Singer

Publication Date: 2020

$20.00

Sweet (CO2) and sour (H2S) corrosion have continuously been a challenge in oil and gas production and transportation. Yet, some key issues are still not well understood, especially at high temperature production conditions. A CO2/H2S ratio of 500, which has been used (often inaccurately) to determine which corrosion mechanism is dominant, is probably even less valid at high temperature. The nature of the corrosion products forming at high temperature in CO2/H2S environments and their effects on the corrosion rate are not known. Finally, the impact on pipeline integrity of environmental changes between sweet and sour production conditions (simulating reservoir souring) has not been well documented. CO2, H2S, and CO2/H2S corrosion experiments were conducted at 120oC to investigate corrosion mechanisms and corrosion product layer formation at high temperature. The results show that the corrosion products were still clearly dominated by H2S under the pCO2/pH2S ratio of 550. Formation of Fe3O4, FeCO3, and FeS corrosion product layers had a direct impact on the measured corrosion rates and was dependent on the gas composition and on the sequence of exposure (CO2 then H2S and vice versa). Compared with H2S corrosion alone, the presence of CO2 could retard Fe3O4 formation in CO2/H2S mixture environment. No obvious change in steady state corrosion rate was observed when the corrosion environment was switched from CO2 to H2S and vice versa.

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The Role of Pyrite in Localized Corrosion of Mild Steel

Product Number: 51317--9251-SG

ISBN: 9251 2017 CP

Author: Jing Ning

Publication Date: 2017

$20.00

The formation of greigite and/or pyrite seems to correlate with onset of localized corrosion Experiments involving deposition of pyrite on the steel surface were conducted to investigate if localized corrosion occurs when pyrite is deposited on mild steel in an aqueous H2S environment.

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51318-11192-Investigation of FeCO3 and FeS Precipitation Kinetics by EQCM

Product Number: 51318-11192-SG

Author: Zheng Ma / Yang Yang / Bruce Brown / Srdjan Nesic / Marc Singer

Publication Date: 2018

$20.00

In the present study, the precipitation kinetics of iron carbonate (FeCO3) and iron sulfide (FeS) were studied over a range of temperatures to gain a better understanding of their effect on corrosion resistance.

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Mechanical Properties of a Mackinawite Corrosion Product Layer

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Mechanical Properties of a Mackinawite Corrosion Product Layer

Fe3O4, FeCO3 or FeS - Which Corrosion Product Will Prevail at High Temperature in CO2/H2S Environments?

The Role of Pyrite in Localized Corrosion of Mild Steel

51318-11192-Investigation of FeCO3 and FeS Precipitation Kinetics by EQCM

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