Corrosion of Pipeline Steel in the Presence of Alternating Current and the New CP Recommendation

2010 ◽  
Author(s):  
A. Q. Fu ◽  
Y. F. Cheng
Keyword(s):  
Corrosion Rate ◽  
Current Density ◽  
Cathodic Protection ◽  
Pitting Corrosion ◽  
Pipeline Steel ◽  
Alternating Current ◽  
National Association ◽  
Ac Current ◽  
Ac Interference ◽  
Full Protection

The alternating current (AC)-induced corrosion of a cathodically protected X65 pipeline steel was studied in a high pH, concentrated carbonate/bicarbonate solution. Results demonstrated that the corrosion rate of the steel increases with the AC current density, and AC interference could increase the pitting corrosion of the steel. In the absence of AC interference or at a low AC current density, i.e., 20 A/m2, a cathodic protection (CP) potential of −950 mV(Cu/CuSO4 electrode, CSE), which is 100 mV more cathodic than −850 mV(CSE) recommended by National Association of Corrosion Engineers (NACE), provides a full protection over the steel. When the AC current density is higher than 20 A/m2, the NACE-recommended CP is incapable of protecting the pipeline from corrosion. A new CP standard is thus developed for recommendation to industry to avoid AC corrosion of pipelines.

scholarly journals Effect of Alternating Current and Sulfate-Reducing Bacteria on Corrosion of X80 Pipeline Steel in Soil-Extract Solution

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 144 ◽  
Author(s):  
Yongchang Qing ◽  
Yunlong Bai ◽  
Jin Xu ◽  
Tangqing Wu ◽  
Maocheng Yan ◽  
...  
Keyword(s):  
Current Density ◽  
Pipeline Steel ◽  
Sulfate Reducing Bacteria ◽  
Alternating Current ◽  
Soil Extract ◽  
X80 Pipeline Steel ◽  
Sulfate Reducing ◽  
Extract Solution ◽  
Ac Current ◽  
Reducing Bacteria

AC corrosion has been considere d as a threat to the corrosion of buried pipelines. Effects of sulfate-reducing bacteria (SRB) and alternating current (AC) on corrosion of X80 pipeline steel in soil-extract solution were investigated by electrochemical and surface analysis techniques. AC current can inhibit the growth of planktonic and sessile SRB. The corrosion current density of steel with 10 mA/cm2 AC current is about nine times bigger than that without AC current. Corrosion morphology changes from small pitting to large pitting holes with increasing AC current density. Corrosion of steel with SRB and AC current is controlled by both active dissolution of iron and film degradation.

A Real-Time AC/DC Measurement Technique for Assessment of AC Corrosion of Buried Pipelines

2012 ◽  
Author(s):  
Cindy X. Su ◽  
Luyao Xu ◽  
Frank Y. Cheng
Keyword(s):  
Real Time ◽  
Current Density ◽  
Steel Surface ◽  
Steel Corrosion ◽  
Buried Pipelines ◽  
Total Potential ◽  
Ac Current ◽  
Potential Alternative ◽  
Current Densities ◽  
Ac Interference

In this work, a real-time AC/DC signal data acquisition (DAQ) technique was developed, which is capable of separating the DC and AC potential components from the recorded total potential, providing mechanistic information about the steel corrosion in the presence of AC interference. It was found that the corrosion of the steel is enhanced by the applied AC current density from 0 to 400 A/m2. With the further increase to 600 A/m2 and 800 A/m2, the corrosion rate of the steel decreases, which is attributed to passivation of the steel at sufficiently high AC current densities, and a compact film is formed on the steel surface. Moreover, the derived mathematic relationships between AC potential and AC current density provides a potential alternative to determine AC current density on pipelines based on measurements of AC potential in the field.

New Cathodic Protection Criteria Based on Direct and Alternating Current Densities Measured Using Coupons and Their Application to Modern Steel Pipelines

CORROSION ◽  
2004 ◽  
Vol 60 (3) ◽  
pp. 304-312 ◽  
Author(s):  
Y. Hosokawa ◽  
F. Kajiyama ◽  
Y. Nakamura
Keyword(s):  
Cathodic Protection ◽  
Field Tests ◽  
Alternating Current ◽  
Pipe Material ◽  
Review Of The Literature ◽  
Density Measurements ◽  
Corrosion Risk ◽  
Ac Current ◽  
Current Densities ◽  
Dc Current

Abstract The risks of alternating current (AC) corrosion, overprotection, and stray direct current (DC) corrosion are increasing on cathodically protected buried steel pipelines due to the recent changes in factors such as burial conditions, the characteristics of coatings, and pipe material. In the present study, field tests as well as a review of the literature on these risks were conducted. As a result, it has been revealed that there is a certain limitation to assess these risks with respect to conventional cathodic protection (CP) criteria based on pipe-to-soil potential. Therefore, new CP criteria for the elimination of these risks have been developed based on DC and AC current density measurements on coupons. The effectiveness of the new CP criteria was evaluated through the design of CP systems on newly constructed pipelines subject to the risks of AC corrosion, overprotection, and stray DC corrosion. Using these new CP criteria, the design and installation of CP systems as well as the elimination of these risks were completed successfully. The risks of overprotection as well as stray DC corrosion were eliminated by providing an appropriate level of DC current from CP rectifiers. The elimination of the AC corrosion risk was accomplished using distributed magnesium anodes and solid-state DC decoupling devices. Finally, the new CP criteria were proven to be effective in eliminating the risks of AC corrosion, overprotection, and stray DC corrosion on buried steel pipelines.

Effects of alternating stray current on the corrosion behaviours of buried Q235 steel pipelines

2017 ◽  
Vol 64 (6) ◽  
pp. 599-606 ◽  
Author(s):  
Yanbao Guo ◽  
Hai Tan ◽  
Deguo Wang ◽  
Tao Meng
Keyword(s):  
Corrosion Rate ◽  
Current Density ◽  
Corrosion Potential ◽  
Rapid Development ◽  
Geometrical Shape ◽  
Uniform Corrosion ◽  
Negative Deviation ◽  
Stray Current ◽  
Content Type ◽  
Ac Current

Purpose With the rapid development of rail transportation and energy-delivery systems, such as buried oil and gas pipelines and high-voltage transmission lines, the alternating current (AC) corrosion of buried steel pipelines is becoming more serious. This paper aims to study the corrosion behaviours of Q235 buried steel pipelines induced by the alternating stray current, with a set of indoor simulated experiment apparatuses. Design/methodology/approach The corrosion of the coating holidays of the buried steel pipelines at various AC current densities from 0 to 200 A/m2 in the soil-simulating environment was revealed by the electrochemical and weight-loss methods. Findings The results showed that the corrosion potential of the steel shifted negatively obviously and the corrosion rate of the steel increased with the increasing of AC current density. At a low AC current density, the negative deviation of the corrosion potential of the steel was small and the increase of corrosion rate was slight. However, the negative deviation of the corrosion potential was remarkable and the corrosion rate was greatly increased at a relative higher AC current density. The geometrical shape of the corrosion images indicated the corrosion forms changed from uniform corrosion to local corrosion due to the increase of AC interference. Originality/value Investigation results are of benefit to provide a new strategy to forecast and evaluate the AC-induced corrosion of the buried pipelines which could improve the safety of pipeline transportation.

Study of Corrosion Behavior of Carbon Steel in Soil under Alternating Current Influence

2011 ◽  
Vol 204-210 ◽  
pp. 1852-1855
Author(s):  
Yan Qiang Liu ◽  
Zhi Shan Liang
Keyword(s):  
Weight Loss ◽  
Carbon Steel ◽  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Cathodic Protection ◽  
Alternating Current ◽  
Steel Sample ◽  
Protection Level ◽  
16Mn Steel

The AC corrosion behavior of 16Mn steel under cathodic protection is investigated by the experiments carried out in labortary. The weight loss test showed that the corrosion rate of 16Mn steel sample under different alteranting voltage interference is influenced greatly by the applied cathodic protection level.

scholarly journals Study on the Electrochemical Performance of Sacrificial Anode Interfered by Alternating Current Voltage

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Qingmiao Ding ◽  
Xiao Chu ◽  
Tao Shen ◽  
Xiaoxiao Yu
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Rate ◽  
Electrochemical Impedance ◽  
Alternating Current ◽  
Open Circuit ◽  
Sacrificial Anode ◽  
Corrosion Control ◽  
Current Voltage ◽  
Ac Interference ◽  
And Diffusion

The effect of alternating current (AC) voltage of 0V, 1V, 3V, and 5V on magnesium alloy sacrificial anode electrochemical properties was studied by open circuit potential (OCP) analysis, electrochemical impedance spectroscopy (EIS), and polarization curve measurements. The results demonstrate that the AC voltage has a great effect on the magnesium alloy sacrificial anode. The corrosion control is anode control in the first two days with no AC interference. The stray current accelerates the transmission and diffusion of oxygen, so the corrosion rate under AC interference is higher than that with no AC interference. And the corrosion control becomes cathodic control under AC interference. The corrosion rate of the sacrificial anode is faster and faster as the AC interference voltage increases in the range of 0~5V, while the corrosion inclination is weakened.

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