Volume 39, Issue 3

Mechanisms for materials degradation are usually inferred from electrochemical measurements and characterization performed before, during, and after exposure testing and/or failure analysis of service materials. Predicting corrosion and other materials degradation modes, such as hydrogen-assisted cracking, from first-principles has generally been limited to thermodynamic predictions from Pourbaix or Ellingham diagrams and the Galvanic series. Using electronic structure calculations, modern first-principles methods can predict ab initio the key rate-controlling processes for corrosion and hydrogen susceptibility as a function of pH, potential, and solution chemistry, and materials composition and microstructure. Herein we review density functional theory (DFT) approaches for studying the electrochemical reactions occurring on fresh metal and alloy surfaces related to environmentally assisted cracking and localized corrosion/pitting. Predicted changes in surface chemistry as a function of the environment were correlated against experimental crack growth rate data obtained for alloys 718, 725, and pipeline steel under electrochemical control. We also review the application of the method to study the effects of alloying on the chloride susceptibility of stainless steels and Ni–Cr-based corrosion-resistant alloys. Perspectives for improving the model are given, and extending it to future fields of application in corrosion science and engineering.

Silica is a chemically inert molecule with an ability of adsorption on the metal to form a layer of barrier for preventing it from the atmospheric damage. However, a larger amount of silica is required for producing the impactful anticorrosive activity, leading to toxic and carcinogenic effects in the environment, and thus limiting the applications of silica. Application of nanotechnology in the synthesis of silica nanocomposites provides, for example, the advantages of better biocompatibility, systemic stability, ineffective response towards pH changes large multifunctionality. However, uses of harmful solvent, low penetration and toxicity, remain the major concerns for silica nanoparticles. Synthesis of silica nanocomposites with green technology will be an attractive approach to offer reduction in toxicity associated with the silica, higher surface area, effective penetration, easy spreadability, better adsorption over the metal surface and also provided the controlled release of chemical agents on contact with metal surface. The present article enlightens the use of green syntheses in the formulation of silica nanocomposites for corrosion inhibition in comparison to conventional synthetic method and provides the insights of various green nanocarriers such as nanocontainers, sol-to-gel nanoparticles, metallic nanostructures and silica nanocomposites for enhancing the proficiency of corrosion inhibition.

Carbon capture and storage (CCS) technology is considered to be one of the key technologies to reduce CO 2 emissions. This paper reviews the industry corrosion accidents of CCS transportation system, in which the pipeline corrosion risk is analyzed, and the pipeline corrosion theory is summarized. Also, the effect of impurities on gas phase properties is discussed. We analyze the corrosion mechanism of multicomponent impurities on metals in a supercritical CO 2 environment from the aspects of corrosion rate and corrosion products. We also describe the mechanism of pitting and stress corrosion of metals in a supercritical CO 2 environment. Besides, the formation mechanism of FeCO 3 protective layer and the research status of corrosion resistant alloys in supercritical CO 2 are reviewed and analyzed. Finally, a series of shortcomings and prospects of the current research are put forward.

In coal fired power plants, the metallic surfaces such as boiler tubes, walls of combustion chambers and other parts degrade by corrosion, erosion and abrasion. It happens due to the hot gaseous environment, steam oxidation and presence of hard minerals and impurities in the coal. It is very important to protect these surfaces from material loss, otherwise it would lead to increased repair and maintenance cost along with decreased plant efficiency. In this paper, the role of thermal spray coatings has been studied for the protection of different steel grades exposed to such degrading conditions at high temperatures, in coal-based power plants. A comprehensive study has been done by analysing and comparing the work done by various researchers. Some recent advancements related to coating materials and modification in coating techniques have also been studied. This paper would be helpful for the researchers to get an idea for selecting an appropriate substrate material and coating material for industrial applications.

Gas boriding was used to produce the borided layer containing a mixture of chromium and nickel borides on the Inconel ® 600-alloy. The borided sample was characterized by a higher corrosion potential (−0.953 V) than the non-borided sample (−1.005 V). The corrosion current density was significantly lower for the borided sample. The oxidation at 1000 °C for 24 h caused the formation of different oxides on the surface of the borided sample. Simultaneously, the presence of nickel and chromium borides was confirmed by XRD analysis after the oxidation test. It was concluded, that the gas boriding could be an effective barrier against corrosion and oxidation of Inconel ® 600-alloy.

To reduce the use of synthetic compounds as wear-corrosion inhibitors, and substitute them with new ecological compounds, we are interested in evaluating the effect of the essential oils against the tribocorrosion. The present paper describes the effect of adding Thymus zygis subsp. gracilis (TZ) essential oil (3 g·L −1 ) on AISI 304L tribocorrosion behavior in 0.5 M H 2 SO 4 . As a result, the addition of this essential oil decreases the tribocorrosion rate [E (%) = 84.38], the value of friction coefficient, and the energy dissipated during sliding wear, in comparison to those recorded for dry environment and 0.5 M H 2 SO 4 . In addition, the essential oil improves the surface morphology of metal as shown by the scanning electron microscopy and energy dispersive X-ray and the three-dimensional optical profiler analysis. In addition, the modeling approaches of experimental results, involving the density functional theory, the electrostatic potential, and the Monte Carlo methods, show that thymol (42.5% of TZ oil) is the best corrosion and tribocorrosion inhibitor that adhered to the stainless steel surface and offers a greater coverage area to block the metal wear-corrosion. According to the obtained results, the TZ essential oil can be used in the food industry to prevent the wear of materials.