As we all know, corrosion of pipelines by hydrogen sulfide is the most worrying factor in the production and transport of oil and gas. In this work the corrosion behavior of API 5L X70MS and X70MO low carbon steels in hydrogen sulfide environments was investigated. Hydrogen induced cracking and sulfide stress cracking tests were carried out according to NACE TM0177 standard. After testing, blisters and cracks were observed only in X70MO steel, probably due to its lower grain refinement and banded microstructure. Internal cracks seem to be initiated in elongated MnS inclusions. Corrosion process was studied by obtaining potentiodynamic polarization curves, which were registered after open circuit potential measurements, at room temperature. Both steels showed general corrosion in NACE 177A solutions, but the corrosion rate values ​​in H2S-saturated solution were about an order of magnitude higher than those ones in deaerated solution. Hydrogen permeation w::as char::acterized in accordance with ASTM G148 standard. In deaerated H2SO4 solution, permeation measurements were similar for both steels. In H2S-saturated solution, X70 MO exhibited higher hydrogen oxidation current values ​​than X70 MS. H2S seems to promote the reduction of protons and increase the concentration of hydrogen atoms in the solution/steel interface, favoring the diffusion process. As X70MO has a coarse microstructure, it offers more pathways for hydrogen diffusion.

The corrosion inhibition effect of Licorice hydroalcoholic extract (Licorice extract) was investigated as a green corrosion inhibitor for API 5L Gr. B carbon steel in CO2 environment, using Tafel polarization and electrochemical impedance spectroscopy (EIS) methods. The results showed that Licorice extract can be effective corrosion inhibitor in the CO2 environment and act as an anodic inhibitor. The measurement data revealed that inhibition efficiency increased with the increase of Licorice extract concentration. Thermodynamic calculations indicated that adsorption behavior of Licorice extract on the steel surface obeys Langmuir adsorption isotherm and Licorice extract physically-chemically adsorbed on the steel surface in which adsorption process was spontaneous.

In this study, the corrosion behavior of carbon steel API 5L Gr.B and injection rate of an Imidazoline-based inhibitor was investigated in Artificial Seawater. For this purpose, after immersion of samples at open circuit potential for 30 min, Tafel polarization and Electrochemical Impedance Spectroscopy (EIS) measurements were done. Tafel polarization curves showed that the minimum values for corrosion current density achieve at 40 ppm concentration of inhibitor. EIS results expressed that maximum values for polarization resistance achieve at 40 ppm concentration of inhibitor and demonstrated an agreement with the Tafel polarization results. Also, EIS results showed that the best electrical equivalent circuit presents two time constants.

Stress corrosion cracking behavior of X52 pipeline steel was investigated in a near neutral pH solution by slow strain rate test, potentiodynamic polarization and surface analysis technique. Potentiodynamic polarization tests were performed at fast and slow potential sweep rates, to simulate crack tip and crack wall roles in the SCC process. The results showed that the dominant mechanism of SCC at relatively low and moderate applied potentials is anodic dissolution mechanism. While, at more cathodic applied potentials hydrogen based mechanism was the dominant one.

In this paper, an uncoupled thermo-mechanical nonlinear FE analysis of submerged arc welding process for straight seam large diameter oil and gas pipes to determine residual stresses is presented. The analysis starts with thermal part where, bi-elliptical Goldak equation is used for applying heat input distribution. Afterward, a certain code checks the elements one by one in order to determine the metallurgical phase transformations during cooling process based on cooling time from 800ºC to 500ºC (t8/5). Then the associated mechanical properties of each element is calculated and assigned to the corresponding element to execute the stress analysis phase. A good agreement is observed between simulation results and experimental results obtained from metallography and hole drilling test method. In addition to the results related to the special case studied in this research, undertaking severe nonlinearities due to phase transformation of the API X70-5L material and defining the equivalent material properties during phase transformation are of the new aspects of this research..

This Research has been Conducted to Investigate the Effect of Preheating Temperature on the Weld Toughness of API 5L X65 Carbon Steel Material. Since the API 5L X65 PSL2 Micro Alloyed Material Is Widely Used in Oil and Gas Refinery Industries, In This Research, We Tried to Investigate the Effect of Preheated Temperature on the Welding Toughness of the Mentioned Steel. In This Research Two Steel Pipes with a Diameter of 46 Inches and a Thickness of 36. 5 mm Were Tested. The Pipes Were Welded With an Arc Welding of Tungsten Electrodes With Neutral Protective Gas (GTAW) and Shield Metal Arc Welding (SMAW) Combination Process Using a Filler Metal ER 80S-G and Electrode E8018-G. Before the Welding Operation, They Were Preheated at a Minimum Temperature of 100 Degree Celsius and a Maximum Temperature of 250 Degree Celsius and Controlled. Then, Charpy Impact Test Was Used to Investigate the Effect of Preheating Temperature on Toughness and Absorption of Welding Energy and a Metallographic Test Was Used to Investigate the Macroscopic and Microstructure of This Steel. Also in This Research, a Hardness Test Was Used to Determine the Hardness of Weld Metal. Based on the Obtained Result, the Controlled Preheated Temperature Due to Mild Cooling Rate Increased the Weld Toughness Properties and The Creation of Coaxial Fine Grains in the Crystalline Structure of the Steel Mentioned and Conversely, Inappropriate and Uncontrolled Preheating Temperature May Increase the Hardness and Strength and Reduce the Amount of Toughness and the Formation of Coarse Grained Columns in the Crystalline Structure Due to the High Cooling Rate. Base on this, it is Concluded That the Weld Metal with a Controlled Preheat Temperature has a Higher Toughness and Resistance to Impact, While Weld Metal with an Uncontrolled Preheat Temperature has Less Toughness and is More Sensitive to Cracking, Especially Hydrogen Cracks.

Fluticasone propionate, a steroid medication commonly used to treat asthma and allergic rhinitis, was evaluated for its potential as a corrosion inhibitor for API 5L Grade B steel in a 3.5% sodium chloride medium. The experimental techniques employed included the gravimetric method, potentiodynamic polarization, electrochemical impedance spectroscopy measurements, and surface analysis. The results demonstrated that fluticasone propionate is an effective corrosion inhibitor, with inhibition efficiencies of 90.10%, 91.86%, and 92.91% as determined by the weight loss method, polarization studies, and the electrochemical impedance spectroscopy technique, respectively. As the inhibitor concentration was increased in the corrosive solution, the charge transfer resistance also increased, due to the growing thickness of the electrical double layer. Polarization data indicated that the drug acted as a mixed-type inhibitor. Adsorption studies confirmed that the adsorption process was spontaneous and involved a physisorption mechanism: adsorption of the drug compounds onto the metal surface followed the Langmuir adsorption isotherm model. An increase in the electrolyte temperature led to a decrease in the inhibition efficiency from 90.10% to 72.45%. A thermodynamic analysis revealed that the addition of the inhibitor led to an increase in the activation energy of the test solution from 6.06 kJ.mol-1 to 31.04 kJ.mol-1, thus confirming the formation of a protective layer that reduced the kinetics of the corrosion reactions. Surface analysis revealed that the inhibited sample showed less deterioration compared to the uninhibited one.