Guar Gum as an Eco-Friendly Corrosion Inhibitor for N80 Carbon Steel under Sweet Environment in Saline Solution: Electrochemical, Surface, and Spectroscopic Studies.

In this study, the corrosion inhibition performance of the natural polysaccharide guar gum (GG) for N80 carbon steel in CO2-saturated saline solution at different temperatures and immersion times was investigated by weight loss and electrochemical measurements. The results have revealed that GG showed good inhibition performance at lower and higher temperatures. The inhibition efficiency observed via weight loss measurements reached 76.16 and 63.19% with 0.4 g L-1 of GG, at 25 and 50 °C, respectively. The inhibition efficiency of GG increased as the inhibitor concentration and immersion time increased but decreased with increasing temperature. EIS measurements have shown that, even after prolonged exposure, GG was still able to protect the metal surface. Potentiodynamic measurements showed the mixed-type nature of GG inhibitive action. The Temkin and Dubinin-Radushkevich adsorption isotherm models give accurate fitting of the estimated data, and the calculated parameters indicated that the adsorption of GG occurred mainly via an electrostatic or physical adsorption process. The associated activation energy (Ea) and the heat of adsorption (Qa) supported the physical adsorption nature of GG. FTIR analysis was used to explain the adsorption interaction between the inhibitor and the N80 carbon steel surface. SEM-EDS and AFM confirmed the adsorption of GG and the formation of an adsorptive layer of GG on the metal surface.

An Insight into the Defects-Driven Plasticity in Ductile Cast Irons.

The microstructure and tensile behavior of two heavy section castings that had chemical compositions typical of GJS400 were investigated. Conventional metallography, fractography, and micro-Computer Tomography (µ-CT) were employed, enabling the quantification of the volume fractions of eutectic cells with degenerated Chunky Graphite (CHG), which was identified as the major defect in the castings. The Voce equation approach was exploited to evaluate the tensile behaviors of the defective castings for integrity assessment. The results demonstrated that the Defects-Driven Plasticity (DDP) phenomenon, which refers to an unexpected regular plastic behavior related to defects and metallurgical discontinuities, was consistent with the observed tensile behavior. This resulted in a linearity of Voce parameters in the Matrix Assessment Diagram (MAD), which contradicts the physical meaning of the Voce equation. The findings suggest that the defects, such as CHG, contribute to the linear distribution of Voce parameters in the MAD. Furthermore, it is reported that the linearity in the MAD of Voce parameters for a defective casting is equivalent to the existence of a pivotal point in the differential data of the tensile strain hardening data. This pivotal point was exploited to propose a new material quality index assessing the integrity of castings.

Influence of High-Pressure Die Casting Parameters on the Cooling Rate and the Structure of EN-AC 46000 Alloy.

The paper presents the results of the research on the impact of process parameters of high-pressure, cold-chamber die casting of an industrial casting made of aluminium alloy on the casting properties assessed macroscopically by measuring the casting average density and microscopically through the characteristics of the casting microstructure. The analysis covers the influence of three selected velocity settings of the pressing plunger, which determine the filling time, and three values of the compression pressure setting characteristic of the third phase of the casting process. The cooling and solidification simulations of the casting were performed using the ProCAST software. During the simulation tests, the impact of the filling rate of the alloy into the die cavity on the cooling rate and the alloy solidification path at selected points were determined. The conducted research allowed linking the process parameters with the parameters of the casting structure with different wall thicknesses. Metallographic examinations of the castings were carried out using a light microscopy, SEM, and EDS analysis. The fraction of the phases α(Al), the size of dendritic cells, and the size of silicon particles, in the cross-sections of the castings with wall thickness of 3, 6, and 11 mm, respectively, were determined.

Effect of CO2 Partial Pressure on the Corrosion Inhibition of N80 Carbon Steel by Gum Arabic in a CO2-Water Saline Environment for Shale Oil and Gas Industry.

The effect of CO2 partial pressure on the corrosion inhibition efficiency of gum arabic (GA) on the N80 carbon steel pipeline in a CO2-water saline environment was studied by using gravimetric and electrochemical measurements at different CO2 partial pressures (e.g., PCO2 = 1, 20 and 40 bar) and temperatures (e.g., 25 and 60 °C). The results showed that the inhibitor efficiency increased with an increase in inhibitor concentration and CO2 partial pressure. The corrosion inhibition efficiency was found to be 84.53% and 75.41% after 24 and 168 h of immersion at PCO2 = 40 bar, respectively. The surface was further evaluated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), grazing incidence X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy (XPS) measurements. The SEM-EDS and GIXRD measurements reveal that the surface of the metal was found to be strongly affected by the presence of the inhibitor and CO2 partial pressure. In the presence of GA, the protective layer on the metal surface becomes more compact with increasing the CO2 partial pressure. The XPS measurements provided direct evidence of the adsorption of GA molecules on the carbon steel surface and corroborated the gravimetric results.

The influence of habitat structure on genetic differentiation in red fox populations in north-eastern Poland.

The red fox (Vulpes vulpes) has the widest global distribution among terrestrial carnivore species, occupying most of the Northern Hemisphere in its native range. Because it carries diseases that can be transmitted to humans and domestic animals, it is important to gather information about their movements and dispersal in their natural habitat but it is difficult to do so at a broad scale with trapping and telemetry. In this study, we have described the genetic diversity and structure of red fox populations in six areas of north-eastern Poland, based on samples collected from 2002-2003. We tested 22 microsatellite loci isolated from the dog and the red fox genome to select a panel of nine polymorphic loci suitable for this study. Genetic differentiation between the six studied populations was low to moderate and analysis in Structure revealed a panmictic population in the region. Spatial autocorrelation among all individuals showed a pattern of decreasing relatedness with increasing distance and this was not significantly negative until 93 km, indicating a pattern of isolation-by-distance over a large area. However, there was no correlation between genetic distance and either Euclidean distance or least-cost path distance at the population level. There was a significant relationship between genetic distance and the proportion of large forests and water along the Euclidean distances. These types of habitats may influence dispersal paths taken by red foxes, which is useful information in terms of wildlife disease management.

Movements of European bison (Bison bonasus) beyond the Bialowieza Forest (NE Poland): range expansion or partial migrations?

The European bison is the largest terrestrial mammal in Europe. After extinction in the wild at the beginning of the twentieth century, it was re-introduced to Bialowieza Forest and other woodlands in Eastern Europe. In this paper, we analysed the movements of European bison beyond the continuous woodlands of the Bialowieza Forest (NE Poland) between 1964 and 2010. In total, 1,117 direct observations of bison were collected. The number of males moving out of the forest fluctuated during the study period, whilst the number of females steadily increased. The number of male observations outside of the forest per annum was dependent on the population size and snow depth, whilst the number of cows in mixed groups moving outside of the forest was correlated with the population size only. Males were observed mainly alone (50 % of observations) or in small groups of two to three individuals (25 %); however, distribution of group size differed from those observed in the population. There was a significant difference between the direction of movement of males and females out of the forest-males moved mainly west and southwest, whilst females moved to the north. This was also significantly different from the expected movement direction. The mean distance of bison observations from the forest border was 1.8 ± 0.13 km and did not differ significantly between sexes. After 1990, males were observed significantly farther away from the forest (2.2 km) than in the previous years (0.9 km). Most observations (94 % of bulls and 93 % of cows) were up to 5 km from the forest edge. The range of bison in the vicinity of the Bialowieza Forest was strictly seasonal. Most observations (78 % in males and 88 % in females) were recorded from November to April. Increasing utilisation of areas beyond the forest habitats may be driven by different factors but most probably it is related to range expansion and the bison's preference for open habitats. The strong seasonal pattern of bison movements indicate that the partial seasonal migrations were initiated in the Bialowieza population.