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Evaluation of Susceptibility of an API 5L X-52 Pipeline Steel to Hydrogen Stress Cracking and Ethanol Stress Corrosion Cracking in Bio-Based Fuel Grade Ethanol Feedstocks

Over the past two decades, bio-based fuel-grade ethanols (BFGEs), derived from a variety of agriculture feedstocks (e.g., corn, sugar cane, soybean oil, and sugar beet), are increasingly being used as a renewable energy source to reduce the dependence of fossil fuels for motor vehicle applications. One cost-effective and environmentally benign way to transport BFGEs is through steel transmission pipelines. However, cases of environmentally assisted cracking (EAC) in the transportation of BFGEs have been documented including some in pipelines.

Product Number: 51323-18794-SG
Author: Jie He, Brent Sherar, Peter Ellis II, Russ Kane
Publication Date: 2023
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Environmentally assisted cracking (EAC) was found on the ID of a cathodically protected API 5L X-52 steel ethanol pipeline buried in a soil environment. To identify the root cause, multiple tests were conducted to evaluate the susceptibility of the steel to externally driven hydrogen stress cracking (HSC) and internally driven ethanol stress corrosion cracking (eSCC).
Hydrogen permeation tests were first conducted to investigate the possibility of HSC occurrence on the steel in a simulated chloride-contaminated soil environment. The atomic hydrogen content in the steel was found to be 0.7 to 2.5 ppm by weight while charging at −1.6 V vs. Cu/CuSO4 electrode (CSE). The cathodic overprotection could drive the surface pH to 14 or higher and cause caustic corrosion in the environment.

Environmentally assisted cracking (EAC) was found on the ID of a cathodically protected API 5L X-52 steel ethanol pipeline buried in a soil environment. To identify the root cause, multiple tests were conducted to evaluate the susceptibility of the steel to externally driven hydrogen stress cracking (HSC) and internally driven ethanol stress corrosion cracking (eSCC).
Hydrogen permeation tests were first conducted to investigate the possibility of HSC occurrence on the steel in a simulated chloride-contaminated soil environment. The atomic hydrogen content in the steel was found to be 0.7 to 2.5 ppm by weight while charging at −1.6 V vs. Cu/CuSO4 electrode (CSE). The cathodic overprotection could drive the surface pH to 14 or higher and cause caustic corrosion in the environment.