Atmospheric corrosion of carbon steel: Results of one-year exposure in an andean tropical atmosphere in Colombia.

In this study was examined the response of carbon steel to atmospheric corrosion after one-year exposure in Valle de Aburrá, a subregion located in northwestern Colombia. The study involved the assessment of material mass loss and corrosion rate, the characterization of atmospheric aggressiveness, and the analysis of the morphology and composition of corrosion products in five different sites. Climatological and meteorological factors were assessed by testing for chloride content, sulfur dioxide levels, and time of wetness (TOW). The analysis of corrosion products was conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. Based on corrosion rates, two sites exhibited a more aggressive environment, with a corrosivity category of C3, while the remaining sites were categorized as C2. The study confirmed the presence of lepidocrocite and goethite phases on the surface of carbon steel at all test sites. Data analysis revealed that both the TOW and the industrial activity significantly influence the corrosion of this metal.

Oxidation mechanism of pyrite in a thiosulfate solution: electrochemical impedance (EIS) and in situ Raman spectroscopy.

Ammoniacal thiosulfate has been used lately as an alternative lixiviant for leaching gold from sulfides ores which are not amenable for cyanidation. However, the oxidation of the sulfide minerals generates products that inhibit the dissolution of gold and can promote the degradation of the leaching solution. The complexity of the ammoniacal thiosulfate leaching system has prevented the unification and clarification of the mechanisms of oxidation of sulfide ores used for gold extraction. In this study, a method combining polarization curves, Electrochemical impedance spectroscopy (EIS), and in situ Raman spectroscopy was implemented to investigate the oxidation process of high-purity pyrite. Pyrite samples were dispersed in carbon paste electrode (CPE-Py). The polarization curves of CPE-Py exhibited an increase in current values for overpotentials greater than 0.1 V, indicating the initiation of mineral oxidation processes. Subsequently, a maximum current was observed initially, followed by subsequent decrease, indicating the occurrence of passivation processes on the electrode surface. Hydrodynamic polarization curves demonstrated that the overpotential at which the passivation process occurs is independent of mass transport, suggesting that the passivation products were formed through solid-state transformation. Impedance spectra revealed that at overpotentials below 0.1 V, a partially resolved capacitive semicircle was observed, which was associated with the resistance encountered when charge was transferred between the solution and the surface layer interface. This resistance decreased as the polarization overpotential increased, implying a decrease in charge transfer kinetics. At higher overpotentials (0.3 V-0.4 V), a second capacitive semicircle appeared, linked to the oxidation of one or several species present in the mineral. In situ Raman spectroscopy was utilized to identify the oxidation species of pyrite in ammonia-thiosulfate ((NH4)2S2O3) leaching solution at a pH = 10.2. The composition of the species varied depending on the applied anodic potential. At low anodic potentials (0.1 V), Fe(OH)2 and thiosulfate (S2O32-) were formed, while at high anodic potentials (0.4 V), iron products such as Fe3O4 and γ-FeOOH, as well as sulfide species including thiosulfate, tetrathionates and sulfates (S2O32-, S4O6-2 and SO42-) were formed.

Atmospheric deterioration of ceramic building materials and future trends in the field: a review.

Multiple techniques have been developed and implemented around the world to monitor structures and minimize the costs of repairing, maintaining, and losing ceramic building materials due to environmental factors. Understanding the different degradation phenomena that affect ceramic building materials and evaluating their condition can help reduce material losses caused by deterioration and the need for interventions. This study reviews the main forms of atmospheric degradation that affect ceramic materials and the commonly employed methods to evaluate their deterioration. The aim is to illustrate the different types of atmospheric deterioration that affect ceramic materials and to demonstrate the current monitoring methods and testing. In addition to a literature review, a bibliometric analysis was conducted to highlight the available tools to counter atmospheric deterioration. The analysis shows that CO2, sulfates, and temperature are the most important types of degradation for ceramic construction materials. It was also discovered that due to their porous nature, ceramic construction materials require careful control as contaminants and water can easily penetrate them. The two most severe types of deterioration identified in this analysis for reinforced concrete were chloride-induced corrosion and carbonation.

Morphological analysis of plasma electrolytic oxidation coatings formed on Ti6Al4V alloys manufactured by electron beam powder bed fusion.

This study investigates and compares plasma electrolytic oxidation (PEO) coatings produced on wrought Ti6Al4V alloy substrates with those resulting from electron beam powder bed fusion (PBF-EB). For a duration of 1000 s, a phosphate/silicate electrolyte with a current density of 50 A/cm2 was employed to fabricate the coatings. Surface and polished cross-sections of the coated specimens underwent SEM and X-ray diffraction (XRD) analyses. The obtained coatings exhibit differences of up to approximately 18% in thickness and formation, as well as in their anatase phase. The anatase phase is present at a level of 54.09% in the substrates processed by PBF-EB and 38.54% in wrought substrates. After 1000 s of PEO, the coatings formed on the wrought substrates exhibited higher porosity and larger pores (>1 µm) compared to those produced on the PBF-EB specimens. The PBF-EB coatings had lower porosity because they contained fewer pores larger than 1 µm. The findings imply that the unique microstructural arrangement of PBF-EB-produced additively made Ti6Al4V materials plays a significant impact in the development and morphological properties of PEO oxide coatings.

Atmospheric corrosion maps as a tool for designing and maintaining building materials: A review.

Atmospheric corrosion maps can be used to conduct a fast and graphical assessment of material deterioration in specific geographic environments. These maps are a key tool for selecting the most adequate materials in terms of corrosion resistance, maintenance, and cost-efficiency in outdoor constructions. Several studies have evaluated the effects of environmental factors and pollutants on building materials at local, regional, national, and international levels. However, not enough atmospheric corrosion maps are readily available, possibly due to the complexity of the variables that should be considered to construct them, which include weather, meteorological, and pollution-related factors that vary in space and time. This article presents a thorough literature review of atmospheric corrosion maps published between 1971 and 2021 mainly indexed in the Scopus database. It is complemented with a detailed review of books, journals, and projects by research centers that focuses on the methodologies, parameters, and tools that have been used to construct said maps. Most of the available maps are outdated, which highlights the need for new maps that reflect recent global changes in atmospheric pollution and temperature that can intensify metal deterioration in some places.

Additive manufacturing of Ti6Al4V alloy via electron beam melting for the development of implants for the biomedical industry.

Additive Manufacturing (AM) or rapid prototyping technologies are presented as one of the best options to produce customized prostheses and implants with high-level requirements in terms of complex geometries, mechanical properties, and short production times. The AM method that has been more investigated to obtain metallic implants for medical and biomedical use is Electron Beam Melting (EBM), which is based on the powder bed fusion technique. One of the most common metals employed to manufacture medical implants is titanium. Although discovered in 1790, titanium and its alloys only started to be used as engineering materials for biomedical prostheses after the 1950s. In the biomedical field, these materials have been mainly employed to facilitate bone adhesion and fixation, as well as for joint replacement surgeries, thanks to their good chemical, mechanical, and biocompatibility properties. Therefore, this study aims to collect relevant and up-to-date information from an exhaustive literature review on EBM and its applications in the medical and biomedical fields. This AM method has become increasingly popular in the manufacturing sector due to its great versatility and geometry control.

Interferon receptor expression in multiple sclerosis patients.

To determine the gene expression of IFNAR1, IFNAR2 and MxA protein and the association with IFNbeta treatment response in MS patients. MS patients treated with IFNbeta had a significant decrease in IFNAR1 and IFNAR2 expression, and a significant increase in MxA compared to non-treated patients and healthy controls. Also, those patients who had a good response to treatment had a significant decrease in IFNAR1 and IFNAR2 expression compared to non-responders, non-treated patients and healthy controls. IFNbeta influences the expression of its receptors, and is greater in patients who respond to IFNbeta treatment. This down-regulation could be indicative of the response to IFNbeta.