Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


Final thesis Lizeth Sanchez.pdf (3.5 MB)

ETD Abstract Container

Abstract Header

"Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection."

Sanchez Camacho, Lizeth J.
http://orcid.org/0000-0002-2347-9304
http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788

Abstract Details

2018, Master of Science, University of Akron, Chemical Engineering.
AC (alternating current) induced corrosion presents a threat to the integrity and safe operation of underground pipelines that share the right-of-way with an interference source, such as high-voltage transmission lines (HVTL) or AC rail transit systems. This phenomenon can accelerate the local corrosion rate in the structure by the superposition of a sinusoidal wave of positive and negative polarization potential onto the cathodic protection potential. Localized corrosion has been found in the failure of pipelines under AC influence. Since stress corrosion cracking (SCC) is likely to initiate in zones of high pit density, environmental assisted cracking could be promoted by the AC interference. Moreover, cathodic reactions on the steel, especially the hydrogen evolution reaction can induce cracking by promoting the absorption of hydrogen into the steel. The effect of AC on the hydrogen embrittlement under applied cathodic protection is currently unknown. In this work, slow strain rate testing (SSRT), and electrochemical hydrogen permeation tests were carried out to investigate the cracking susceptibility of low carbon steels (1018 and API X65) under the combination of AC voltages and cathodic protection potentials in a simulated soil solution (NS4). The synergistic effect of cathodic potentials (-0.77, -0.85, and -1.12 V vs. SCE) and AC interference (1, 2, and 3 V rms) was systematically studied. The loss of plasticity and brittle behavior was more evident when more negative cathodic potentials were applied to the samples. The SSRT results demonstrated that the AC interference had a deleterious effect on the ductility and mechanical properties of the low carbon steel, increasing its SCC susceptibility. Corrosion products deposited on the surface were found to increase with an increase in the AC voltage and intensive pitting was observed at a lower cathodic potential with AC interference. In addition, scanning electron microscopy (SEM) examination revealed changes in the fracture morphology. Ductile fracture with small dimples was mainly observed at less negative cathodic potential without AC interference, while cleavage planes and microcracks, characteristic of brittle fracture, increased with higher AC voltage and current densities. The brittle fracture presented under the AC interference was associated with anodic dissolution and/or hydrogen embrittlement mechanism. The hydrogen permeation tests were performed in a Devanathan-Stachurski cell, according to the ASTM G148 standard. Hydrogen diffusivity and sub-surface concentration of atomic hydrogen were calculated. Higher sub-surface hydrogen concentration was obtained at lower cathodic potential. The presence of AC voltage further increased the hydrogen permeation current, indicating more hydrogen adsorption on the steel surface and therefore possibly promoting embrittlement
Hongbo Cong (Advisor)
R.Scott Lillard (Committee Member)
David M. Bastidas (Committee Member)
114 p.
Chemical Engineering
AC corrosion; stress corrosion cracking; pitting; hydrogen permeation

Recommended Citations

Citations

  • Sanchez Camacho, L. J. (2018). "Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection." [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788

    APA Style (7th edition)

  • Sanchez Camacho, Lizeth. "Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection.". 2018. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788.

    MLA Style (8th edition)

  • Sanchez Camacho, Lizeth. ""Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection."." Master's thesis, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788

    Chicago Manual of Style (17th edition)

akron1531157966071788
415
© 2018, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.