Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(AC corrosion). Showing records 1 – 3 of 3 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


University of Akron

1. Sanchez Camacho, Lizeth J. "Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection.".

Degree: MS, Chemical Engineering, 2018, University of Akron

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 Advisors/Committee Members: Cong, Hongbo (Advisor).

Subjects/Keywords: Chemical Engineering; AC corrosion; stress corrosion cracking; pitting; hydrogen permeation

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Sanchez Camacho, L. J. (2018). "Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection.". (Masters Thesis). University of Akron. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788

Chicago Manual of Style (16th Edition):

Sanchez Camacho, Lizeth J. “"Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection.".” 2018. Masters Thesis, University of Akron. Accessed September 19, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788.

MLA Handbook (7th Edition):

Sanchez Camacho, Lizeth J. “"Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection.".” 2018. Web. 19 Sep 2019.

Vancouver:

Sanchez Camacho LJ. "Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection.". [Internet] [Masters thesis]. University of Akron; 2018. [cited 2019 Sep 19]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788.

Council of Science Editors:

Sanchez Camacho LJ. "Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection.". [Masters Thesis]. University of Akron; 2018. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788

2. Κιούπης, Νικόλαος. Επίδραση των επαγόμενων τάσεων στην καθοδική προστασία μεταλλικών αγωγών στο έδαφος.

Degree: 2009, National Technical University of Athens (NTUA); Εθνικό Μετσόβιο Πολυτεχνείο (ΕΜΠ)

The present Ph.D. dissertation deals with the study of the ac induced voltage interference on the C.P. operation and impact on C.P. effectiveness concerning the anti-corrosion protection of buried-in-soil metallic pipelines. The measurements were performed under real conditions on the main pipeline of Greek Natural Gas grid, extending from Greek-Bulgarian border to Revithoussa islet in Attiki region, as well as on its several pipeline branches. The 50Hz ac voltage level on the pipeline is attained by the inductive interference from the close proximity and/or parallelism primarily with high voltage overhead power transmission lines and secondly with ac electrified railways. During the periodic inspection and monitoring of C.P. operation and maintenance on the transmission pipelines of the Natural Gas grid of Greece, ac interference caused by inductive effects of overhead high voltage powerlines as well as from dc and/or quasi-dc stray currents, especially telluric currents have been discovered. According to the initial design, at various sites along the pipeline route, overvoltage arresters had been connected across pipeline and earth electrodes. These overvoltage arresters, consisting of a set of antiparallel thyristors, are activated by ac voltage threshold level of 25V, a limit considered as a safety barrier for prevention from electric shock. The overvoltage arresters allowed pipeline to attain high ac induced voltage level (up to 25 V) for long time intervals, thus resulting in a high likelihood for corrosion caused by alternating currents (ac corrosion). In addition, this high ac interference level caused variations of dc potential and dc current. For the effective ac mitigation without degrading the pipeline cathodic protection function, special ac mitigation equipment, named Alternating Voltage Arresters Continuing Function (AVACF), were designed, constructed and installed at selected pipeline locations. AVACF were designed for conducting ac current while simultaneously effectively blocking dc current. After AVACF installation, C.P. system operation was significantly improved with the exception of instant-off C.P. pipe-to-soil potential readings falsification due to AVACF capacitor discharging currents. This phenomenon was thoroughly studied via an electric equivalent circuit simulating the system pipeline connected to earthing electrodes through capacitive equipment (e.g. AVACF). The effect of every parameter involved was investigated with regard to the falsification of instant-off potential readings. The most critical factors affecting the falsification of instant-off potential readings were disclosed and measures for minimising the instant-off potential readings error were suggested. Based on the results of the cathodic protection measurements used for inspection of C.P. system function, an improved modification of the test method for electrical isolation efficiency of installed insulating couplings was suggested. Various ac corrosion mechanisms and corrosion from telluric stray currents were discovered,…

Subjects/Keywords: Επαγόμενες τάσεις; Τελλουρικά ρεύματα; Ρεύματα διαφυγής; Σωληναγωγοί; Διάβρωση από εναλλασσόμενο ρεύμα; Καθοδική προστασία; Εκτονωτής υπερτάσεων; Induced ac voltage interference; Telluric currents; Stray currents; Pipeline; Ac corrosion; Cathodic protection; Overvoltage arrester

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Κιούπης, . . (2009). Επίδραση των επαγόμενων τάσεων στην καθοδική προστασία μεταλλικών αγωγών στο έδαφος. (Thesis). National Technical University of Athens (NTUA); Εθνικό Μετσόβιο Πολυτεχνείο (ΕΜΠ). Retrieved from http://hdl.handle.net/10442/hedi/17964

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Κιούπης, Νικόλαος. “Επίδραση των επαγόμενων τάσεων στην καθοδική προστασία μεταλλικών αγωγών στο έδαφος.” 2009. Thesis, National Technical University of Athens (NTUA); Εθνικό Μετσόβιο Πολυτεχνείο (ΕΜΠ). Accessed September 19, 2019. http://hdl.handle.net/10442/hedi/17964.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Κιούπης, Νικόλαος. “Επίδραση των επαγόμενων τάσεων στην καθοδική προστασία μεταλλικών αγωγών στο έδαφος.” 2009. Web. 19 Sep 2019.

Vancouver:

Κιούπης . Επίδραση των επαγόμενων τάσεων στην καθοδική προστασία μεταλλικών αγωγών στο έδαφος. [Internet] [Thesis]. National Technical University of Athens (NTUA); Εθνικό Μετσόβιο Πολυτεχνείο (ΕΜΠ); 2009. [cited 2019 Sep 19]. Available from: http://hdl.handle.net/10442/hedi/17964.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Κιούπης . Επίδραση των επαγόμενων τάσεων στην καθοδική προστασία μεταλλικών αγωγών στο έδαφος. [Thesis]. National Technical University of Athens (NTUA); Εθνικό Μετσόβιο Πολυτεχνείο (ΕΜΠ); 2009. Available from: http://hdl.handle.net/10442/hedi/17964

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Akron

3. Ghanbari, Elmira. Corrosion Behavior of Buried Pipeline in Presence of AC Stray Current in Controlled Environment.

Degree: PhD, Chemical Engineering, 2016, University of Akron

Cathodic protection (CP) and other corrosion mitigation strategies to preserve the integrity of pipelines are reported have failed in the presence of AC. This type of failure is a threat for catastrophic failure and there is a lack of well-agreed mitigation criteria for it. AC grounding systems as well as "consensus" standards that recommend limits on the maximum allowable AC current density and critical ratios of AC and CP currents are the only available techniques for preventing AC corrosion. Unclear mechanism of AC corrosion is the main reason for the uncertainty on the CP criteria in the presence of AC interference. AC interference can occur by conduction or induction mechanism where pipelines share right of way with some interference sources such as a high-voltage transmission line typically fed by a high voltage line at 50 or 16.7 Hz frequency. The goal of this work is to understand the mechanism of AC induced corrosion by studying the effects of AC interference on steel at different DC potentials.This work consists of two phases. In the first phase, the influence of simultaneous presence of different AC and DC potentials on corrosion rate of API grade X65 pipeline steel by performing both electrochemical techniques and weight loss analysis in sodium chloride solution was studied. Experimental test results showed that the effect of AC is most pronounced near the open circuit potential; at more positive potentials the rates approach those of the ohmic drop/mass transport-limited DC rates. Correspondingly, at negative potentials the rates decrease. Surprisingly, at all potentials, it was found that the AC corrosion rate was equal to the average AC current in the system. The data generated from weight loss experiments were compared with the results from a model for AC corrosion that was developed using a modified Butler-Volmer approach. The model considers the anodic and cathodic Tafel slopes, diffusion limited oxygen transport, interfacial capacitance and solution resistance. The model was used to explain the observation that the AC corrosion rate was equal to the average AC current in the system. Both experimental and model results showed the importance of the solution resistance and interfacial capacitance on the rate of AC corrosion, especially at the frequency of 60Hz or higher.As it relates to the pipeline, one of the factors that influences this interfacial capacitance is the composition of the soil around the pipeline. For example, alkaline earth mineral content of the soil such as calcium or magnesium base minerals produce calcareous deposits on the coating fault. In the second phase of this project, the influence of the solution resistance and interfacial capacitance on the rate of AC corrosion was investigated in more detail. This was done by performing AC experiments in both extracted soil environment and soil simulated solution. Additionally, artificial scales were grown on X65 pipeline steel, which were then exposed to different AC and DC potentials in a soil-simulating solution. These films were… Advisors/Committee Members: Lillard, Robert Scott (Advisor).

Subjects/Keywords: Engineering; Materials Science; Chemical Engineering; AC interference on pipelines, corrosion, carbon steel, scale formation, interfacial capacitance

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Ghanbari, E. (2016). Corrosion Behavior of Buried Pipeline in Presence of AC Stray Current in Controlled Environment. (Doctoral Dissertation). University of Akron. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=akron1475677625895234

Chicago Manual of Style (16th Edition):

Ghanbari, Elmira. “Corrosion Behavior of Buried Pipeline in Presence of AC Stray Current in Controlled Environment.” 2016. Doctoral Dissertation, University of Akron. Accessed September 19, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1475677625895234.

MLA Handbook (7th Edition):

Ghanbari, Elmira. “Corrosion Behavior of Buried Pipeline in Presence of AC Stray Current in Controlled Environment.” 2016. Web. 19 Sep 2019.

Vancouver:

Ghanbari E. Corrosion Behavior of Buried Pipeline in Presence of AC Stray Current in Controlled Environment. [Internet] [Doctoral dissertation]. University of Akron; 2016. [cited 2019 Sep 19]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=akron1475677625895234.

Council of Science Editors:

Ghanbari E. Corrosion Behavior of Buried Pipeline in Presence of AC Stray Current in Controlled Environment. [Doctoral Dissertation]. University of Akron; 2016. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=akron1475677625895234

.