51316-7520-Evaluation of Steel API X70 Embrittlement in Different Ethanol Environments

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Product Number: 51316-7520-SG

ISBN: 7520 2016 CP

Author: Joseane Ortiz Breitenbach

Publication Date: 2016

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In recent years there have been significant increases in ethanol production due to Brazilian Alcohol Program (Pro-álcool) implementation Kyoto Protocol and replacement MBTE (methyl-tert-buthyl ether) in some countries. The world’s largest producers of ethanol are United States and Brazil being produced from Corn and Sugar Cane correspondingly. Pipeline transportation is the most cost effective in large volumes however in USA there are evidences that ethanol may have caused stress corrosion cracking (SCC) in pipelines and also in storage tanks. This phenomenon can be assessed for example by slow strain rate tests (SSRT) and fracture toughness tests with specimens well defined by international standards. This study aims to evaluate the susceptibility of steel API 5L X70 in different ethanol environments (SFGE – Simulated Fuel Grade Ethanol Corn and Sugar Cane) through SSRT technique using traditional and fracture mechanics specimens. The tests were carried out on notched specimens according to standard NACE TM 0111 and pre-cracked C(T) (Compact Tension) specimens according to ASTM E647-08. The C(T) specimens analysis was performed using linear elastic fracture mechanics equations. The traditional SSRT showed very similar results for SFGE and Corn environments evidencing the aggressiveness of both. The analysis of K-R curves initially presented a decrease in toughness only in Corn environment however the K for crack initiation and fractography investigation confirm the material embrittlement in both SFGE and Corn ethanol environments.