Environmentally assisted degradation of spinodal copper alloy C72900

•Examination of the resistance against i) SSC/SCC in H2S environment and ii) HSC under cathodic protection for UNS C72900.•Testing done according to ISO 15156-3 Level V and NACE TM0177 in H2S solution, and with polarised samples under constant load in 3.5% NaCl solution.•Severe cracks observed on 4-...

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Bibliographic Details
Published in:Corrosion science 2018-09, Vol.142, p.45-55
Main Authors: Johnsen, Roy, Lange, Torstein, Stenerud, Gaute, Olsen, Jim Stian
Format: Article
Language:English
Subjects:
Cathodic polarization
Cathodic protection
Copper
Copper base alloys
Corrosion
Corrosion mechanisms
Corrosion resistance
Cracks
De-alloying
Degradation
Electrode polarization
Hydrogen embrittlement
Hydrogen sulfide
Seawater
Stress corrosion
Stress corrosion cracking
Stress cracking
Sulfide cracking
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Summary:•Examination of the resistance against i) SSC/SCC in H2S environment and ii) HSC under cathodic protection for UNS C72900.•Testing done according to ISO 15156-3 Level V and NACE TM0177 in H2S solution, and with polarised samples under constant load in 3.5% NaCl solution.•Severe cracks observed on 4-point bend samples exposed to H2S at 150 °C, while no fracture was seen on samples exposed to cathodic protection.•EDS analysis exhibited evidence of selective corrosion and depletion of Cu in the cracked regions indicating SCC for the samples exposed to H2S.•UNS C72900 is resistant against HSC, but cannot be used in environment corresponding to ISO 15156-3 Level V. In this work, a spinodal Copper alloy – C72900, was tested to investigate the resistance against environmentally assisted degradation. The material was tested according to ISO 15156-3 Level V in sour H2S solution and to cathodic polarization in simulated seawater with stressed samples. The results showed no indications of hydrogen stress cracking under cathodic polarization in seawater. However, cracks up to 3 mm deep were found on the samples exposed to sour H2S environment. Energy Dispersive Spectroscopy showed severe depletion of copper close to the cracks which is associated with selective corrosion. Stress corrosion cracking was the dominating crack mechanism in the ISO 15156-3 Level V test.
ISSN:0010-938X
1879-0496
DOI:10.1016/j.corsci.2018.06.031