Volumen 67 (2023): Edición 1 (May 2023)

Manganese-based coatings on AZ31 magnesium alloy with Mg(OH)₂ interlayer were prepared by hydrothermal reaction under different process conditions (temperature, time, and concentration). The harsh reaction conditions provided coatings with defects. These defects enabled the corrosive environment penetrated to the magnesium alloy which impaired the corrosion properties of AZ31 alloy. Optimal conditions included a temperature of 120 °C, 0.25 M MnCl₂, and a reaction time of 1 h. The prepared coating was mainly composed of Mn₃O₄, which consisted of nanosized crystals of polyhedral shape. Potentiodynamic polarization measurements showed that the coating had very good corrosion resistance in 0.15 M NaCl. Future work will focus on the potential use of the manganese-based coating in biomedical applications.

This study aims to analyze the influence of process parameters used for hydrothermal synthesis of CaP coatings on their properties and to improve their corrosion resistance and biocompatibility compared to the substrat AZ31. The parameters monitored were deposition time, pH of the reaction mixture, and concentration of precursors in the reaction mixture. For the deposited CaP coatings on AZ31 magnesium alloy, the surface morphology and the number of structural defects were evaluated using scanning electron microscopy. Electrochemical corrosion properties were evaluated using polarization techniques in Hank’s solution. The results showed that the best properties were obtained for the sample prepared in a reaction mixture at 120 °C, pH 5 for a deposition time of 120 min, when the concentration of precursors in the reaction mixture was 0.30 mol/l Ca(NO₃)₂·4H₂O and 0.28 mol/l NH₄H₂PO₄. Under these conditions, the best electrochemical corrosion properties were achieved.

Indoor conditions have the greatest influence on the long-term storage of historical artefacts. The following text summarizes essential knowledge regarding the evaluation of the corrosivity of indoor atmospheres with an emphasis on the effect of the presence of volatile organic acids on corrosion of lead. It provides an overview of the information and resources necessary to decide whether lead storage conditions are safe and concludes by outlining a path to resolution if they are not.

With the aim of saving CO₂ in cement production, various approaches are currently being pursued in the development of new materials. One possibility is to reduce the ratio of clinker to cement by using supplementary cementitious materials (SCMs). Some SCMs like fly ash or granulated blast furnace slag have been used successfully in cement for a long time and their use is covered by standards. Since the availability of these materials cannot be ensured in the long term, alternative additives are also being tested. The results presented here were obtained as part of a joint research project that was carried out in cooperation with the Bauhaus University Weimar. In this study, three different SCMs are investigated with regard to their effect on the corrosion of steel embedded in mortars: A metakaolin, a metaillite, and a modified steel mill slag were each tested at a proportion of 30 wt.% in a CEM I reference cement. In the two-stage tests, the passivation behavior of steel in mortars was first investigated in electrochemical tests. Based on this, tests were carried out in leached solutions of the different binders with different Cl–/OH– ratios.

The results show that all the blended types of cement investigated provide passivation of the steel in mortar. The use of the calcined clays metakaolin or metaillite resulted in higher polarization resistances and lower passive current densities as well as increased electrical resistivities, especially for metakaolin. The steel in mortar with the steel mill slag showed comparable electrochemical behavior to the OPC mortar. The tests in leached solutions slightly indicate a higher corrosion-inducing Cl–/OH– ratio when using metakaolin or steel mill slag.

AA5083 alloy exhibits favorable resistance to corrosion and welding characteristics, making it attractive for application in the marine environment. However, pitting and intergranular corrosion of AA5083 is still troublesome. This study investigates the corrosion resistance and texture evolution of friction stir processed AA5083 alloy with Cerium Oxide (CeO₂) as reinforcement. The FSP trials were performed by varying the process parameters: tool rotation speed (TRS), tool traverse speed (TTS), and a constant shoulder diameter (SD). The fabricated surface composite (FSC) specimens were subjected to microstructure, microhardness, intergranular corrosion, and electrochemical corrosion analysis. The specimens were subjected to advanced analytical instruments such as TEM, EBSD, and XRD to study the microstructure and texture evolution. The results showed that the corrosion of AA5083 alloy in the saline environment is highly suppressed by reinforcing it with cerium oxide (CeO₂) using friction stir processing, as it acted as a good corrosion inhibitor.

The penetration and diffusion of chloride ions into reinforced concrete structures is the primary cause of steel reinforcement corrosion; thus, this work focused on demonstrating and reviewing the beneficial effects of green inhibitors and organic inhibitors on chloride-induced corrosion. Another motivation for selecting and testing these types of inhibitors was to investigate their effectiveness in greater depth using a variety of various scientific methodologies and a variety of very advanced laboratory and materials testing procedures. In this method, the chosen eco-friendly inhibitor (so-called green inhibitor) might be compared with at least a less hazardous inorganic inhibitor, which is also cheap and usually effective in mitigating iron corrosion in the given environment.

The human organism is under normal circumstances a stable system. The values of traceable chemical and biochemical markers change within a known and often very narrow range. In orthopedics an inflammatory disorder after the implantation can occur. The presence of such a problem demonstrates itself, even in the initial phase, in a drop of pH. A pH sensor, which would be temporarily allocated close to the implant, could therefore instantly indicate the origin of the inflammatory process. The behaviour of tantalum as a pH indicator was studied in this work. In the tested range of pH (4.5-7.5), the potential-pH dependence of this sensor was determined to be at the approximately Nernstian level –59 mV/pH. The main drawback was the long-term initial stabilization of the signal. The only meaningful detection method that could be used in practice is the electrochemical potential-pH dependence monitoring.