Volume 42, Issue 1

2,5-Bis(4-dimethylaminophenyl)-1,3,4-oxadiazole (DAPO), 2-acetylthiophene thiosemicarbazone (2-AT), 2-hydroxyphenyl-5-mercapto-1-oxa-3,4-diazole (HMO), and 2-cinnamyl-5-mercapto-1-oxa-3,4-diazole (CMO) have been studied by measurement several quantum chemical parameters such as E HOMO , E LUMO , bandgap energy, softness, hardness, electrophilicity, nucleophilicity, and Fukui function analysis. The best corrosion inhibition efficiency was evaluated through a comparison between theoretical and experimental results. In gas and aqueous phases, protonated and nonprotonated species were investigated for their electronic structures in order to discover the factors and reasons behind corrosion inhibition. A theoretical study of all the studied compounds in gas and aqueous phases was investigated by employing the density functional theory (DFT) at 6–311++G(d, p) basis set and Becke’s three parameters hybrid exchange–correlation functional (B3LYP). The molecules are calculated using quantum computational chemistry calculations such as Gaussian09 software. The experiments were carried out on carbon steel and HCL. Carbon steel is the most often used steel because it combines outstanding mechanical qualities with a low cost. One of the most commonly utilized agents for these purposes is HCl solution. On the other hand, steel and ferrous alloys are likely to corrode under certain conditions. One of the most effective strategies for protecting metals against corrosion is corrosion inhibitors, and they are becoming more common.

Electro-chemo-mechanical properties of anodic oxide (passive) films formed on metals have been reviewed focusing on the results of stress variations caused by anodic oxidation of Cu, Ni, and Fe thin film electrodes in deaerated pH 8.4 borate buffer solution at 25 °C. The surface stress varies toward compressive direction due to adsorption of OH on Cu from aqueous solution as well as adsorption of oxygen on metals from gas phase. The stresses are generated with the growth of three-dimensional anodic oxide films on metals. The magnitude and sign (tensile or compressive) of the intrinsic film stress were determined by taking the residual stress of the substrate and the dielectrostriction into consideration. The tensile or compressive intrinsic film stress depends on p-type or n-type semiconductive properties of the anodic oxide films, which is explained in terms of the void formation or oxide formation in the metal side at the metal/film interface. Furthermore, the stress variation toward compressive direction during cathodic reduction of the anodic oxide films is explained in terms of the volume expansion due to the formation of intermediate species.

Tribocorrosion is getting more and more popular in biomaterials research. The synergism between wear and corrosion is creating deviations from the expected real-world results from individual corrosion or wear studies. The host body consisting of immune system and dissolved proteins makes them highly corrosive which makes the material selection a unique and challenging process for implant materials. The synergism between corrosion and wear leads to shorter implant life. The research on tribocorrosion has bought an insight into this phenomenon and presented ideas to arrest the premature failure of implants. This review focuses on the recent developments in tribocorrosion research and the effectiveness of remedial actions suggested by them. The influence of materials, processing methods and post-processing treatments are also reviewed in detail.

Nuclear power plants (NPPs) have been affected by various failures through corrosion which causes economic losses, increased chance of the radiation exposure and environmental risk. One of the major durability issues in reinforced concrete is the corrosion of reinforcement which significantly reduces the life of reinforced concrete. Considering the increasing demand for longer service lives of NPPs, and the high cost involved in building and maintaining it, adequate preventive measures should be followed to minimize the corrosion. This review majorly discusses about the mechanism of corrosion of steel in NPP structures with emphasis on the mechanisms relevant to NPPs, possible reasons for the concrete corrosion as well as potential failure happening in NPPs. The majors reason for the concrete corrosion in nuclear power plants are mainly corrosive external and internal environment, thermal and mechanical stress, moisture content, microorganisms and stray electrical currents. The corrosion of NPPs may result in loss of structural integrity and leakage of radioactive material. The review also discusses about various corrosion prevention and protection techniques against concrete corrosion and concludes with an overview of present methods and possible future perspectives used to enhance the efficiency of concrete corrosion mitigation methods with focus of NPPs.

In order to meet the development needs of deep-sea oil and gas resources, deep-sea corrosion coupon tests were carried out in the South China Sea, the Western Pacific Ocean, and the Indian Ocean, which can provide a strong guarantee for the rationality of material selection of oil and gas pipelines, platforms and other facilities. In-depth studies were conducted on the environmental adaptability of typical carbon steel and low alloy steel materials after exposure for one year in the deep-sea environment of different sea areas. The main environmental factors affecting deep-sea corrosion behavior were also collected and analyzed. The results showed that the corrosion morphology of carbon steel and low alloy steel in deep sea environment was more uniform than that in the shallow seawater. With the increase of seawater depth, the evolution law of their corrosion rates in different sea areas was similar, with an obvious decline of corrosion rate in the beginning. The gray correlation results indicated that it was mainly controlled by temperature and dissolved oxygen. The high hydrostatic pressure had limited effect on accelerating the deep sea corrosion rate of carbon steel and low alloy steel, but it promoted the formation of more uniform corrosion morphology.

Effects of minor alloying elements (Si, Mn, and Al) on the corrosion resistance behaviors of stainless steel (SS) modified 310S used as a cathode current collector (CCC) material for molten carbonate fuel cells (MCFC) were examined in a mixture of 62 mol% Li 2 CO 3 –38 mol% K 2 CO 3 at 650 °C by measuring the change in corrosion potential and the potentio-dynamic, potentio-static polarization responses. The corrosion potential of modified 310S gradually increased after 9 h of immersion due to an active to passive transition and that of SSs added with minor alloying elements drastically increased before 6 h of immersion due to the reactive alloys. Si, Mn, and Al addition to base SS led to a decrease in corrosion resistance due to the rapid corrosion rate at the cathode operation potential, −40 mV, of the MCFC. The steady state current densities of SSs added with minor alloying elements were higher than that of 310S and modified 310S. Addition of Si, Mn, and Al induced a decrease in corrosion resistance of CCC materials in molten carbonate fuel cell operating temperatures, 650 °C.

The influence of specific microstructural characteristics on the properties of single-pass welding joints was assessed by optical processed images, transmission electron microscopy, microhardness measurements and corrosion tests conducted in various regions of the heat-affected zone (HAZ) in a lean duplex stainless steel. The welded joints were obtained with heat inputs of 1.5 and 2.5 kJ/mm using a gas metal arc welding (GMAW) process with a shielding gas enriched in Ar. Three selected regions in the HAZ showed different ferrite grain sizes and austenite fractions. The place in the welded joint where the HAZ was narrowest, and therefore experiences the highest cooling rate, is most prone to the formation of cubic CrN metastable nitrides. Conversely, the place where the HAZ was wider promotes the precipitation of stable Cr 2 N nitrides with more coalesced intragranular austenite (IGA) particles, where presumably random interfaces predominate. The HAZ region where the cooling rate was the highest presented more pitting corrosion resistance.

Corrosion-electrochemical behaviour of steel E 235 in borate buffer solution (pH = 7.4) containing F − ions with and with no added ZnNTP as an inhibitor, where NTP = N(CH 2 PO 3 ) 3 , was studied by the potentiodynamic polarization and depth-profiling XPS analysis of specimens polarized at different potentials applied. Depending on the potential applied, F − ion was shown to influence differently on the formation, composition and structure of passive film. At E  < 0.1–0.2 V/SSCE, F − ion promotes the passivation via forming sparingly soluble FeF 2 , and the resulting film is comprised of mainly iron(II) oxides and hydroxides, as well as sparingly soluble FeF 2 and FeZnNTP. At E  > 0.1–0.2 V/SSCE, F − ion works for the destruction of the passive film by forming soluble compounds with Fe 3+ ions, which leads to its thinning. ZnNTP inhibitor forms FeZnNTP heterometallic complex with iron ions, which is the most stable constituent of the passive film. When F − ion concentration does not exceed 1.4 mmol/L, ZnNTP inhibitor is optimal to be added in amount of 0.5–1.0 g/L, whereas concentrations of 5.6 mmol/L F − ion and higher require 5 g/L ZnNTP or even more to be added.