The Role of Electrochemical Conditions in Near-Neutral pH SCC Initiation Mechanism(s)

2010 ◽  
Author(s):  
Abdoulmajid Eslami ◽  
Mohammadhassan Marvasti ◽  
Weixing Chen ◽  
Reg Eadie ◽  
Richard Kania ◽  
...  
Keyword(s):  
Cathodic Protection ◽  
Pipeline Steel ◽  
Synergistic Effects ◽  
Co2 Concentration ◽  
Initiation Mechanism ◽  
Ph Values ◽  
Neutral Ph ◽  
Comprehensive Test ◽  
Disbonded Coating

In order to improve our understanding of near-neutral pH SCC initiation mechanism(s), a comprehensive test setup was used to study the electrochemical conditions beneath the disbonded coatings in cracking environments. In this setup the synergistic effects of cyclic loading, coating disbondment, and cathodic protection were considered. Our previous results showed that there can be a significant variation in the pH of the localized environment under the disbonded coating of pipeline steel. The pH inside the disbondment can change significantly from near-neutral to high pH values, strongly depending on the level of cathodic protection and CO2 concentration. Both of these variables affected the electrochemical conditions on the steel surface and therefore the initiation mechanisms. This work highlights the role of electrochemical conditions in near-neutral pH SCC initiation mechanisms.

Stress Corrosion Crack Initiation in X-65 Pipeline Steel Under Disbonded Coating With Cathodic Protection

2008 ◽  
Author(s):  
Bingyan Fang ◽  
Abdoulmajid Eslami ◽  
Richard Kania ◽  
Robert Worthingham ◽  
Jenny Been ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Cathodic Protection ◽  
Pipeline Steel ◽  
Seasonal Fluctuation ◽  
General Corrosion ◽  
Cathodic Current ◽  
Pipe Surface ◽  
Neutral Ph ◽  
Wide Range ◽  
Disbonded Coating

A novel testing setup has been used in this study to simulate crack initiation in X65 pipeline steel exposed to near-neutral pH soil environment. This test setup was designed to simulate synergistic interactions of cathodic current with soil environments underneath the disbonded coating on the pipe surface. It was found from the simulations that the local environment underneath the disbonded coating can be very acidic or alkaline, instead of near-neutral pH as commonly believed, depending on seasonal fluctuation in CO2 level and cathodic current. There exists a wide range of corrosion conditions on the steel surface up the gradient of cathodic current underneath the disbonded coating. General corrosion was found to increase as CP current diminishes. Pitting corrosion in terms of number of pits and size of pits was found to be the most severe at locations where cathodic protection was nearly diminished. These locations had also developed some crack like-defects, which were usually elongated in a direction perpendicular to the loading axis and appeared to be formed from a linkage of neighboring pits and by enhanced corrosion at stress raisers.

scholarly journals EIS analysis on stress corrosion initiation of pipeline steel under disbonded coating in near-neutral pH simulated soil electrolyte

2016 ◽  
Vol 110 ◽  
pp. 23-34 ◽  
Author(s):  
Y.A.N. Maocheng ◽  
X.U. Jin ◽  
Y.U. Libao ◽  
W.U. Tangqing ◽  
S.U.N. Cheng ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Pipeline Steel ◽  
Corrosion Initiation ◽  
Neutral Ph ◽  
Disbonded Coating ◽  
Eis Analysis

Stress corrosion cracking initiation under the disbonded coating of pipeline steel in near-neutral pH environment

2010 ◽  
Vol 52 (11) ◽  
pp. 3750-3756 ◽  
Author(s):  
A. Eslami ◽  
B. Fang ◽  
R. Kania ◽  
B. Worthingham ◽  
J. Been ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Pipeline Steel ◽  
Corrosion Cracking ◽  
Neutral Ph ◽  
Disbonded Coating

Effect of CO2 and R-ratio on near-neutral pH stress corrosion cracking initiation under a disbonded coating of pipeline steel

2011 ◽  
Vol 53 (6) ◽  
pp. 2318-2327 ◽  
Author(s):  
A. Eslami ◽  
R. Kania ◽  
B. Worthingham ◽  
G.V. Boven ◽  
R. Eadie ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Pipeline Steel ◽  
Corrosion Cracking ◽  
Neutral Ph ◽  
Ph Stress ◽  
R Ratio ◽  
Disbonded Coating

Effect of cathodic protection on corrosion of pipeline steel under disbonded coating

2009 ◽  
Vol 51 (9) ◽  
pp. 2242-2245 ◽  
Author(s):  
X. Chen ◽  
X.G. Li ◽  
C.W. Du ◽  
Y.F. Cheng
Keyword(s):  
Cathodic Protection ◽  
Pipeline Steel ◽  
Disbonded Coating

STRESS CORROSION CRACK INITIATION BEHAVIOR FOR THE X70 PIPELINE STEEL BENEATH A DISBONDED COATING

2012 ◽  
Vol 48 (10) ◽  
pp. 1267 ◽  
Author(s):  
Zhiying WANG ◽  
Jianqiu WANG ◽  
En-hou HAN ◽  
Wei KE ◽  
Maocheng YAN ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Stress Corrosion ◽  
Stress Corrosion Crack ◽  
Pipeline Steel ◽  
X70 Pipeline Steel ◽  
Disbonded Coating

Synergistic Methodology Based on Ion Exchange and Biodegradation Mechanisms Applied for Metal Complex Dye Removal from Waste Waters

2018 ◽  
Vol 69 (1) ◽  
pp. 38-44
Author(s):  
Nicoleta Mirela Marin ◽  
Olga Tiron ◽  
Luoana Florentina Pascu ◽  
Mihaela Costache ◽  
Mihai Nita Lazar ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Synergistic Effects ◽  
Freundlich Isotherm ◽  
White Rot ◽  
White Rot Fungus ◽  
Basic Anion Exchange Resin ◽  
Km Value ◽  
Points Of View ◽  
Basic Anion

This study investigates the synergistic effects of ion exchange and biodegradation methods to remove the Acid Blue 193 also called Gryfalan Navy Blue RL (GNB) dye from wastewater. Ion exchange studies were performed using a strongly basic anion exchange resin Amberlite IRA 400. The equilibrium was characterized by a kinetic and thermodynamic points of view, establishing that the sorption of the GNB dye was subject to the Freundlich isotherm model with R2 = 0.8710. Experimental results showed that the activated resin can removed up to 93.4% when the concentration of dye solution is 5.62�10-2 mM. The biodegradation of the GNB was induced by laccase, an enzyme isolated from white-rot fungus. It was also analyzed the role of pH and dye concentration on GNB biodegradation, so 5�10-2 mM dye had a maximum discoloration efficiency of 82.9% at pH of 4. The laccase showed a very fast and robust activity reaching in a few minutes a Km value of 2.2�10-1mM. In addition, increasing the GNB concentration up to 8�10-1 mM did not triggered a substrat inhibition effect on the laccase activity. Overall, in this study we proposed a mixt physicochemical and biological approach to enhance the GNB removal and biodegradability from the wastewaters and subsequently the environment.

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