scholarly journals Analysis of Hydrogen Permeation Through Pipeline Steel in Near-Neutral pH SCC Environments

2000 ◽  
Author(s):  
Yufeng Cheng ◽  
Lin Yang ◽  
Fraser King
Keyword(s):  
Organic Material ◽  
Hydrogen Permeation ◽  
Pipeline Steel ◽  
Open Circuit ◽  
Permeation Flux ◽  
Concentration Boundary ◽  
Sulfate Reducing ◽  
Neutral Ph ◽  
Disulphonic Acid ◽  
Reducing Bacteria

The Devanathan-cell technique has been used to determine the permeation flux of hydrogen through X-65 steel at the open-circuit potential in solutions associated with near-neutral pH stress corrosion cracking. The effects of organic material and microbial activity were also simulated by suitable additions to the solution. A model based on a constant-concentration boundary condition was found to fit the experimental data better than one based on a constant flux condition. The addition of 9,10-anthroquinone-2,6-disulphonic acid to the solution to simulate the effect of organic material lowered the hydrogen permeation flux. Sulfide additions to simulate the action of sulfate-reducing bacteria initially increased the rate of hydrogen permeation, but subsequently resulted in a decrease in permeation current. The hydrogen permeation rate measured on the original oxide-covered surface is lower and more variable than that on polished surfaces. Corrosion rate measurements were also made, from which the fraction of atomic hydrogen diffusing through the specimens was estimated. The results are discussed in terms of the mechanism of hydrogen evolution and absorption.

Hydrogen Permeation Behavior of X-70 Pipeline Steel in a Near-Neutral pH Soil Environment

2000 ◽  
Author(s):  
Weixing Chen ◽  
Sheng-Hui Wang ◽  
Fraser King ◽  
Tom R. Jack ◽  
Martyn J. Wilmott
Keyword(s):  
Boundary Conditions ◽  
Hydrogen Permeation ◽  
Pipeline Steel ◽  
Soil Environment ◽  
Diffusible Hydrogen ◽  
Concentration Boundary ◽  
Hydrogen Flux ◽  
Neutral Ph ◽  
Best Fit ◽  
Galvanostatic Conditions

This paper reports the hydrogen permeation behavior of an X-70 pipeline steel in a synthetic near neutral pH field solution under both galvanostatic and potentiostatic conditions. The hydrogen flux through the steel exposed to the solution is influenced by the chemical reactions at the steel surface on the charging side. Results from tests done under potentiostatic and galvanostatic conditions were compared to predictions based on different boundary conditions assumed in solving Fick’s diffusion equations. Constant concentration boundary conditions gave the best fit. It was also found that the diffusible hydrogen generated in a near neutral pH soil environment is likely to be 3 to 10 times lower than the minimum hydrogen concentration required to initiate hydrogen blistering in pipeline steels.

scholarly journals Effect of Sulfate-Reducing Bacteria (SRB) on the Corrosion of Buried Pipe Steel in Acidic Soil Solution

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 625
Author(s):  
Lijuan Chen ◽  
Bo Wei ◽  
Xianghong Xu
Keyword(s):  
Soil Solution ◽  
Steel Surface ◽  
Pipeline Steel ◽  
Electrochemical Techniques ◽  
Sulfate Reducing Bacteria ◽  
Acidic Soil ◽  
Microbiologically Influenced Corrosion ◽  
Soil Environment ◽  
Sulfate Reducing ◽  
Reducing Bacteria

The influence of sulfate-reducing bacteria (SRB) on the corrosion behaviors of X80 pipeline steel was investigated in a soil environment by electrochemical techniques and surface analysis. It was found that SRB grew well in the acidic soil environment and further attached to the coupon surface, resulting in microbiologically influenced corrosion (MIC) of the steel. The corrosion process of X80 steel was significantly affected by the SRB biofilm on the steel surface. Steel corrosion was inhibited by the highly bioactive SRB biofilm at the early stage of the experiment, while SRB can accelerate the corrosion of steel at the later stage of the experiment. The steel surface suffered severe pitting corrosion in the SRB-containing soil solution.

Microstructural Feature Analysis of X65 Steel Exposed to Ripple Load Testing Under Near Neutral pH Conditions

2014 ◽  
Author(s):  
Pellumb Jakupi ◽  
Bill Santos ◽  
Wilfred Binns ◽  
Ivan Barker ◽  
Jenny Been
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Pipeline Steel ◽  
Open Circuit ◽  
Electron Back Scatter Diffraction ◽  
Corrosion Cracking ◽  
Load Testing ◽  
Neutral Ph ◽  
X65 Steel ◽  
Ph Conditions

Newly designed miniature Compact Tension (CT) specimens, designed according to standard ASTM dimension ratios, and machined out of previously in-service X65 pipeline steel were exposed to super-imposed cyclic loading at high mean stresses in NS4 solution to determine the behaviour of X65 steel to ripple loading under near neutral pH conditions. Electron Back-Scatter Diffraction (EBSD) was used to study the microstructural grain geometry to determine if it influences stress-corrosion cracking (SCC) initiation and propagation. Prior to ripple load testing, finely polished X65 surfaces were subjected to EBSD measurements to characterize the microstructure’s geometry; i.e., grain and grain boundary orientations and texture. On the same locations where EBSD maps were recorded, a grid of cross-shaped resist markings — approximately 1–5 μm in size — were deposited every 15 μm across the analyzed surfaces. Following microscopic analyses the specimens were pre-cracked and re-examined to determine whether the crack initiation procedure preconditions the residual strain (quantified by grain misorientations) around an induced crack. Then, ripple load testing at stress levels characterized by load ratios (R) greater than 0.9 was performed, while simultaneously monitoring the open-circuit potential (OCP) at room temperature. The originally characterized surface was again re-examined to determine if the crack tip propagated preferably along a specific crystallographic grain orientation by comparing the shifts in each cross-shaped grid. Results from this investigation will help determine if there is a link between microstructural grain geometries and transgranular stress corrosion cracking.

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