Search results

The purpose of this paper is to study the effect of chemical composition on the selective oxidation on the surface of bake hardenable steel, and on the surface of modified bake hardenable steel with titanium addition, annealed at different dew points.

The subject scope of the paper is the selective oxidation. The methodology used is the annealing of steels at different dew points, and the surface characterization by using atomic force microscopy, X‐ray photo electronic spectroscopy, and glow discharge optical emission spectroscopy.

The modified bake hardenable steel showed a higher oxidized area than the bake hardenable steel. The optimum condition for annealing of the bake hardenable steel was at 800°C with −30°C dp and −60°C dp as selective oxidation is less voluminous.

One suggestion for future works is the use of transmission electron microscopy for the evaluation of selective oxidation on the steel surfaces.

One practical implication is the determination of the optimum condition for annealing of the bake hardenable steel in the steel plant, decreasing the selective oxidation and increasing the quality of galvanized steels. Another implication is the discard by the steel industry of the development of the modified bake hardenable steel.

The originality of the present work is to use advanced surface analysis techniques to quantify the selective oxidation on the surface of commercial steels. The selective oxidation on the surface of steels must be minimized in order to increase the wet ability of zinc layer on the steel surface.

The purpose of this study was to select an atmospheric corrosion evaluation methodology and to establish a range of relative corrosion penetration and/or progress values, which could be used as reference in the selection of materials for the civil construction industry.

Salt spray, field tests, accelerated cyclic tests and accelerated field tests were used to evaluate atmospheric corrosion resistance of civil construction materials. The cyclic accelerated test and the field test with saline solution spray were found to be appropriate for atmospheric corrosion resistance evaluation.

The corrosion resistance of aluminium killed mild steel, aluminium killed copper added steel, and electrogalvanized steels, all phosphatized and painted, were evaluated by field and accelerated corrosion tests. Of the materials studied, aluminium killed mild steel showed the least resistance to atmospheric corrosion. The use of aluminium killed copper added steel is recommended for material specification in the civil construction industry.

Salt sprays are not adequate to evaluate atmospheric corrosion resistance. There are other cyclic tests that could be tested in future work.

Brazilian technical standards, which specify the metallic materials used in the civil construction industry, will be changed in order to include the construction steel corrosion resistance evaluation methodology, which is proposed in this paper. As a result, the tendency of the construction materials lifetime is set to increase.

This paper contributes to the improvement of the Brazilian Technical Standard by the inclusion of an atmospheric corrosion resistance requirement.

The purpose of this study is to evaluate the quality of organometallic coatings of automotive fuel tanks. Galvannealed steels and galvannealed steels coated with organometallic layers were analyzed using accelerated corrosion tests.

The characterization of galvannealed and organometallic coatings was done by mass (layer removal and weighing) and layer thickness (glow discharge optical emission spectroscopy and scanning electron microscopy), chemical composition (energy dispersive spectroscopy) and surface morphology (scanning electron microscopy). The accelerated corrosion tests were performed in accordance with SAE J2334 and GMW 14872 standards.

The samples tested using the GMW 14872 standard were more deteriorated as compared to the samples submitted to the SAE J2334 test because of the higher degree of aggressiveness of the GMW 14872 test. Despite the presence of white rust, the corrosion resistance of organometallic-coated steel samples was higher as compared to the resistance of galvannealed steel samples.

The organometallic coating is a commercial product, whose chemical composition is confidential.

This study reinforces the quality of automotive tanks with organometallic coating and helps to increase their competitiveness in the market tanks as compared to polymeric tanks.

The study contributes to increase the competitiveness of steel tanks against polymeric tanks that meet the technical requirements but are not environmentally friendly because they are multi-layered and cannot be recycled.

The novelty of this study is the comparison of the corrosion resistance of galvannealed steel tanks and galvannealed steel tanks with organometallic coatings. This corrosion evaluation joined with the physical and chemical characterization was not found in literature and is relevant to the materials selection of the automotive industry.

This study aims to investigate the role of aluminium (Al) in marine environment and the corrosion mechanism of galvalume coatings by conducting accelerated experiments and data analysis.

Samples were subjected to accelerated corrosion for 136 days via salt spray tests to simulate the natural conditions of marine environment and consequently accelerate the experiments. Subsequently, the samples were examined using various test methods, such as EDS, scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS), and the obtained data were analysed.

Galvalume coatings comprised interdigitated zinc (Zn)-rich and dendritic Al-rich phases. Corrosion was observed to begin with a Zn-rich phase. The primary components of the corrosion product film were Al₂O₃ and Zn₅(OH)₈Cl₂·H₂O. It was confirmed that the role of Al was to form a dense protective film, thereby successfully blocking the entry of corrosive media and protecting the iron substrate.

This study provides a clearer understanding of the corrosion mechanism and kinetics of galvalume coatings in a simulated marine environment. In addition, the role of Al, which is rarely mentioned in the literature, was investigated.

The purpose of this paper is to introduce the reader to the nature of confirmatory bifactor modelling. Confirmatory bifactor modelling is a factor analytic procedure that allows researchers to model unidimensionality and multidimensionality simultaneously. This method has important applications in the field of criminal psychology.

This paper begins by introducing the topic of factor analysis and explains how confirmatory bifactor modelling is similar yet distinct to the more familiar factor analytical procedures in the psychological literature.

Through practical examples this paper explains the value of this analytical technique to researchers in criminal psychology. Examples from the existing criminal psychological literature are used to illustrate the way in which bifactor analysis allows important theoretical questions to be addressed.

This paper highlights the strengths and limitations associated with traditional “restricted” confirmatory bifactor models and introduces the notion of the “unrestricted” bifactor model. The unrestricted bifactor model allows greater flexibility for addressing interesting research questions. The paper concludes by providing the reader with an annotated Mplus syntax file for how to perform confirmatory bifactor modelling.

A computational implementation of the production flow analysis, a software named GROUPTEC, for a small company has been proposed. Using GROUPTEC, a case study has been devised and applied to a company, belonging to aluminium‐manufactured products branch. Four analyses of the production flow have been performed, that is, the factory flow analysis; group analysis; line analysis, and tool analysis. After the above technique application, the final results related to the technological cells and their components; part families and machinery groups lead to an adequate cell arrangement, with a grouping efficiency of approximately 98.8 per cent. A productivity gain of 30 per cent has been estimated with the time in movement of parts and queuing at the machine.

This paper aims to report the influence of hexamethylenetetramine (HMTA) on phosphate coatings formed on AZ31 magnesium alloys.

These phosphate coatings were obtained by immersing magnesium alloys in phosphate baths with HMTA. The morphology and composition of the phosphate coatings were investigated via scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction.

The phosphate coatings were mainly composed of CaHPO₄·2H₂O. The HMTA concentration in the phosphate bath influenced the crystallization and corrosion resistance of the phosphate coating.

The polarization curve shows that the anti-corrosion qualities of the phosphate coating were optimal when the HMTA concentration was 1.0 g/L in the phosphate bath. Electrochemical impedance spectroscopy (EIS) shows that the electrochemical impedances increased gradually when the HMTA concentration varied from 1.0 to 3.0 g/L.

This study aims to develops a new-type low-alloy corrosion resistant steel containing Sb and investigate the corrosion mechanism of this new-type low-alloy steel.

Energy dispersive spectrometer, X-ray photoelectron spectroscopy, X-Ray diffraction and scanning electron microscopy were used to evaluate the corrosion resistance of the rust layers formed on these samples. Laser confocal microscopy was used to observe the corroded surfaces of the steels.

Results showed that Sb added can consume H⁺ in the solution, thereby preventing the oxygen reaction to slow down the corrosion rate. Meanwhile, a stable and insoluble substance (Sb₂O₃) in the acidic solution would be produced when the reaction of the product of Sb and H⁺ with the enough dissolved oxygen in the solution. Due to the precipitation of Sb₂O₃ and iron oxyhydroxides, the rust layer of Sb-containing steel became more uniform and compact, which resulted in better corrosion resistance in acid environment.

In this study, a new-type acid resistant low-alloy steel containing Sb was developed. Compared with the results, the corrosion mechanism of the new-type low-alloy steel in acid environment was discussed.

With increasing marine resource development, the rapid development of the marine economy, and the continuous decline of the marine natural resource system, the contradiction between marine resources and economic development is becoming increasingly acute. The study of marine resources and economic development has become a hot and challenging issue in marine resource economics research in recent years. The purpose of this study is to analyze the current situation of marine resources and to realize the sustainable use of marine resources.

This study systematically reviews and analyzes the current status of research on marine resources and economic development issues in four main aspects: marine resource management, marine resources and economic growth, marine resources and economic security, and marine resource accounting in the field of marine resource economics.

It is found that compared to the current status of research on land-based resources and economic development, there is a significant lag in both theoretical construction and methodological innovation in marine resources and economic development.

The purpose of this study is to systematically grasp the current status of marine resources research, promote the coordinated development of marine resources and economic growth, and then realize the safe and sustainable development and utilization of marine resources.

This study aims to identify the relation between perceived learning opportunities, behavioral intentions to voluntarily stay or leave technology organizations and employee retention within these organizations.

This is a survey of 440 employees of a technology organization.

Learning opportunities perceived by managers and technicians presented significant positive correlations with the intention to stay and significant negative correlations with the intention to leave the organization. No relation was identified between perceived learning opportunities and manager retention. Among technicians, the correlation between perceived learning opportunities and retention was near zero.

If the organization wants to guarantee the intention of professionals to stay in the organization, the “perceived learning opportunities” indicator should have a similar level of importance as other objective indicators, such as performance and achievement.

To the best of the authors’ knowledge, this is the first study to identify relations between perceived learning opportunities and behavioral intention to stay and leave of professionals that work in technology organizations.