Synergism Of Hydrogen Research Articles

Synergism of Hydrogen and Oil Composition in Noncatalytic Upgrading of Petroleum Residues

Synergism of hydrogen and composition of oils in noncatalytic upgrading of different petroleum residues were analyzed. Residues were upgraded under temperature of 400°C and initial pressure of 4 MPa for 20 min in the presence of hydrogen or nitrogen, respectively. In addition, anthracene was used as chemical probe to quantify the hydrogen-donating ability of the three feedstocks and the contribution of hydrogen gas. Results show that hydrogen has better synergism with the residue that contains more naphthenic aromatic structure, heteroatom, and metals. Moreover, hydrogen activation possibilities limit the effect of the hydrogen solubility of the oils on upgrading.

Corrosion of Welded X100 Pipeline Steel in a Near-Neutral pH Solution

In this work, electrochemical corrosion behavior of a welded X100 pipeline steel was studied in a near-neutral pH solution by electrochemical scanning vibrating electrode technique combined with metallographic and scanning electron microscopy/energy dispersive x-ray analysis. Results demonstrated that a softening phenomenon occurs around the weld, and there is the high micro-hardness in base steel adjacent to weld. In particular, there is the highest micro-hardness in base steel containing acicular ferrite and bainite. Therefore, welding and the associated post-treatment on X100 steel alter dramatically the microstructure and mechanical property around weld, resulting in an enhanced micro-hardness in base steel. There are high and low local dissolution current densities at base steel and the welded zones, respectively. The difference between the maximum and minimum dissolution current densities decreases with time, and the distribution of dissolution current density tends to be uniform. Hydrogen-charging changes the local dissolution activity of the welded steel. Different from the hydrogen-free steel, there is the highest dissolution current density at heat-affected zone. It is reasonable to assume that the charged hydrogen would accumulate at heat-affected zone, and the synergism of hydrogen and local stress results in a high anodic dissolution rate.

Thermodynamically modeling the interactions of hydrogen, stress and anodic dissolution at crack-tip during near-neutral pH SCC in pipelines

A thermodynamic model was developed to clarify the interactions of hydrogen, stress and anodic dissolution at crack-tip during near-neutral pH stress corrosion cracking in pipelines by comprehensively considering the electrochemical reactions occurring in the pipeline steel in deoxygenated, near-neutral pH solution. By analyzing the change of the free-energy of steel due to the presence of hydrogen and stress, it is demonstrated that a synergism of hydrogen and stress promotes the cracking of steel. The enhanced hydrogen concentration in the stressed steel significantly accelerates the crack growth. An exact expression of the hydrogen concentration factor, i.e., the dependence of anodic dissolution rate of steel at crack-tip on the hydrogen concentration, is essential at the quantitative prediction of the crack growth rate.

Fundamentals of hydrogen evolution reaction and its implications on near-neutral pH stress corrosion cracking of pipelines

In this work, electrochemical techniques were utilized to investigate the hydrogen evolution reaction on X-70 pipe steel and the hydrogen permeation through the steel in near-neutral pH environmental condition. The results demonstrate that the steel has always been in an active-dissolution state in near-neutral pH solution and there is no film formed on the steel surface. Hydrogen evolution is inhibited by anodic polarization of the steel, which is attributed to the alternation of hydrogen evolution mechanism and kinetics on the anodially polarized steel. Combined with slow strain rate tensile tests, it is found that the high susceptibility of steel to stress corrosion cracking (SCC) is always associated with a high hydrogen permeation current. A thermodynamic model was developed, by analyzing the change in free-energy of the steel in the presence and absence of hydrogen and stress, to determine the interactions of hydrogen, stress and anodic dissolution at the crack-tip. The role of hydrogen involvement in pipeline near-neutral pH SCC could be determined quantitatively by characterizing the effect of hydrogen concentration on the dissolution rate of steel and the synergism of hydrogen and stress to promote crack growth.