Abstract The use of natural additives in biodiesel has been investigated, however, there is limited information in the literature in relation to their influence on corrosion resistance and oxidative stability. This work aims to investigate the oxidative stability of biodiesel and the corrosion resistance of carbon steel (AISI 1020) in contact with soybean biodiesel solutions (B100) in the presence and absence of natural additives such as: rosmarinic acid, curcumin, gingerol, eugenol, thymol and quercetin. Corrosion and microscopy tests were used to assess corrosion resistance. The Rancimat technique was used to study oxidative stability. The results obtained indicate that curcumin was the best additive in relation to oxidative stability, while rosmarinic acid showed better performance in inhibiting corrosion. The effect of these substances is related to the presence of phenolic compounds or the existence of oxygen in its molecular structure.

Electric-arc furnace dust (EAFD) is a by-product of steel production and recycling. This fine-grained material contains high amounts of zinc and iron as well as significant amounts of potentially toxic elements such as lead, cadmium and chromium. Therefore, the treatment and stabilization of this industrial residue is necessary. Concrete is a well-known suitable environment for stabilization/solidification of materials which have leachable elements in need of fixation. The effect of the EAFD content on the mechanical and chemical performance of Portland cement concrete is investigated in this paper. The effect of the EAFD content on the setting time of cement slurry was also analyzed. The axial compressive strength of the concrete samples increases with the EAFD addition in the range of 10 to 20 wt. (%) EAFD; also the tensile strength increases with the EAFD addition. An increase in EAFD content significantly increases the setting time of the concrete. The acetic acid leaching and water solubilization tests indicate low mobility of the potentially toxic elements from the EAFD concrete composite. The results of the immersion tests show that the addition of EAFD to the concrete seems to reduce chloride penetration, which may help prevent pitting corrosion in reinforced concrete.

In the present work the effect of substituting Mo with Nb on the glass forming ability and corrosion resistance of Fe-Co-Cr-M-Si-B-Y (M=Mo, Nb) ribbons with high corrosion resistance is investigated. The X-ray powder diffraction pattern indicates that the alloy containing both Nb and Mo presented greater glass forming ability than the alloy containing either of these elements separately. The results obtained indicate that Mo is more effective in enhancing corrosion resistance than the Nb in 4.0 M HCl solution. The alloy containing both Nb and Mo presented greater overall corrosion resistance than the alloy containing only one of these elements.

Abstract This work investigates the effect of the addition of glycerol on the microstructure, corrosion resistance, and efficiency of the electrodeposition process of Cu coating in an acid sulphate solution. The morphology and microstructures of electrodeposits were analyzed using Scanning Electron Microscopy (SEM), Spectrometry X-Ray Diffraction (XRD) and laser scanning confocal microscopy (LSCM). Evaluation of the corrosion resistance was performed in 2.0 mol⋅L−1 NaCl by means of weight loss tests and electrochemical techniques. The addition of glycerol resulted in a decrease in grain and crystallite sizes, a decrease in roughness and an increase in the tensile strain of the coating. The deposition efficiency and the corrosion resistance increased with the addition of glycerol exhibiting a maximum value at the concentration of 0.42 mol⋅L−1, increasing the efficiency of electrodeposition by approximately 96%. This is related to the roughness of the coating, which is minimal at this concentration.

Abstract The Zn coatings obtained through electrodeposition are used to protect steel substrates from corrosion. In general, organic additives are added to the deposition bath in order to improve deposition characteristics such as corrosion resistance, hardness and deposition efficiency. Despite of the literature present information about the various organic additives effects on Zn coating properties there is no analysis of organic compounds with free electron-containing radicals, such as formic acid and cyclohexylamine. The formic acid has oxygen atoms with free electrons, whereas cyclohexylamine contains nitrogen with free electrons. Aiming at overcoming this gap, this manuscript presents an analysis of the effect in addition of formic acid mixture and cyclohexylamine on the deposition flow efficiency, corrosion resistance, hardness, roughness and micro-structure of Zn coating on carbon steel AISI 1020. The corrosion resistance evaluation was performed by potentiodynamic polarization determined by polarization resistance and weight loss tests as well. The analisys of morphology and electrodeposited microstructures were made by the Scanning Electron Microscopy (SEM) and Spectrometry X-Ray Diffraction (XRD). The Zn coatings were obtained from chloride deposition baths at constant pH 5. Results showed that corrosion resistance in the 0.5 mol/L NaCl solution of Zn coatings increases with the addition of the mixture of the formic acid and / or cyclohexylamine. Also, the corrosion resistance is higher with mixture than with additives alone. The addition of the mixture formic acid and cyclohexylamine increases the basal plane presence (0 0 2). However, the basal plane presence (0 0 2) does not increase when formic acid and cyclohexylamine are added alone which indicates a synergic effect of formic acid and cyclohexylamine in in the plan promotion (0 0 2). Also, was observed that an addition of formic acid mixture and cyclohexylamine increases the current deposition efficiency, decreases the roughness and raises the Zn coating hardness.