Volume 36, Issue 6

Corrosion resistance of stainless steels is significantly compromised in oxygen-deficient environments, leading to limited service life as well as unsatisfactory performance of the structures made of these alloys. Cathodic modification with ruthenium has been demonstrated to remarkably improve the corrosion resistance of stainless steels in reducing acidic media, even in the presence of an abrasive suspension. Although ruthenium is several times cheaper than other platinum group metals (PGMs), alloying with ruthenium remains prohibitively more expensive than alloying with conventional, although less effective, metals. A number of strategies have been explored to reduce the amount of ruthenium required to cathodically modify stainless steels in a bid to make this cheaper option much cheaper and thus increase the cost-benefits of using these alloys. Some of the strategies include partially substituting ruthenium with cheaper metals, as well as introducing the PGM as a surface alloy.

Mild steel (MS) corrosion is a worldwide issue that greatly affects the industrial and natural environment. To extend the lifespan of appliances, the control of MS corrosion is necessary. To shield MS from corrosion, specifically from acidic conditions, one of the practical and finest approaches is the application of inhibitors. Triazole derivatives are eco-friendly corrosion inhibitors (CIs) having inconsequential toxicities, excellent inhibition efficiencies (IEs) against corrosion of MS, and extremely high cost-effectiveness. This critical review discusses the general effect of temperature, concentration, time after the application of CI, and type of acid on the IE of triazole derivatives. Further, the review provides an adequate amount of information about the features of excellent CIs; a summary of the reported properties of triazole-based inhibitors, CIs in industries, and current requirements of industries; and recommendations and implications for researchers to improve IE. Additionally, the review also illustrates the mechanisms of action and the IEs, which are evaluated from potentiodynamic polarization parameters, in various acidic media and concentrations of triazole inhibitors. By IE correlation with numerous concentrations and acidic conditions, this review is advantageous and helpful for synthetic chemists to expand the diversity and complexity of a class of triazole derivatives by synthesizing new triazole derivatives.

Electrodeposition and stripping of Zn, Mn and Ni metals and their alloys were investigated in an aqueous sulfate solution. The effect of coating processes and its impact on the substrate were evaluated by investigating the prepared alloys with X-ray diffraction analysis, scanning electron microscopy and atomic absorption spectroscopy. The electrodeposition mechanism of the Zn-Ni-Mn alloy was found to be an anomalous type. The high corrosion resistance of the Zn-Ni-Mn alloy, as well as its preferable surface appearance, has been ascertained compared with the electrodeposited Zn-Ni alloy under homogeneous conditions. It was found that Mn can be codeposited with Ni or with Ni and Zn understudied conditions where it does not deposit in its pure form. During electrodeposition of manganese alone or manganese alloys, a dark brown deposit was formed on the counter platinum electrode surface as a result of oxidation to manganese dioxide.

Presence of moisture is very important for vegetable oils and for corresponding biodiesel because it may cause some problems or accelerate some issues that cannot be ignored. One of the main hindrances of biodiesel is its hygroscopic nature, which accelerates the corrosion of the fuel system of the engines. Thus, this study aims to investigate the effects of moisture on corn biodiesel and its susceptibility to corrosion on different automotive materials such as copper and mild carbon steel. Static immersion tests in corn biodiesel (B100) with different water concentrations (100 ppm, 500 ppm, and 700 ppm) were carried out at 90°C for 1200 h, and the results were compared to that of commercial diesel fuel (B0). After immersion tests, the surface morphology was studied by scanning electron microscopy (SEM), and corrosion products were detected by X-ray diffraction (XRD). The total acid number (TAN) was used to evaluate the changes in acidity of fuel, before and after immersion tests. It was found that under experimental conditions, corn biodiesel is more corrosive than diesel fuel, and the moisture from corn biodiesel has a strong influence on corrosion rate on metals. Copper is more susceptible to corrosion in corn biodiesel than mild carbon steel.

In this study, an addition reaction occurred between epoxidized soybean oil and 4-(dimethylamino)benzenethiol to produce a thiol adduct (TA). The produced TA had been emulsified using a nonionic emulsifier blend (Tween 20, Span 20, and Span 80) to be a water-miscible emulsified thiol adduct (ETA). The ETA emulsion was investigated as a corrosion inhibitor for API X52 carbon steel in 1 m HCl using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. The surface morphologies of the carbon steel were characterized by scanning electron microscopy and energy dispersive X-ray. The effect of temperature was investigated. It was found that the emulsified adduct behaves as an excellent corrosion inhibitor with high inhibition efficiency of 94.7% with 0.005 m concentration. The polarization data indicate that the emulsified adduct acted as a mixed-type inhibitor. The adsorption of the emulsified adduct on the carbon steel surface has been found to follow the Langmuir isotherm.