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The objective of this study was to evaluate the influence of sterilization on a hybrid coating obtained from a sol composed of alkoxysilane tetraethoxysilane (TEOS) and organoalkoxysilane methyltriethoxysilane (MTES) containing 10% (mass) of hydroxyapatite particles. The coating was obtained by dip coating, by applying two layers (protective/bioactive), which were cured at different temperatures (450°C and 60°C). The effects of sterilization on the superficial, electrochemical, bioactive, and mechanical properties of the coating were evaluated by performing different sterilization processes, namely, steam autoclave, hydrogen peroxide plasma, and ethylene oxide. Subsequently, the coating was characterized by using scanning electron microscopy (SEM/FEG), and FTIR measurements were performed to characterize the chemical structure. The bioactivity and degradability of the coating were analyzed by mass variation after immersion in SBF and X-ray diffraction (XRD) analysis. The electrochemical behavior was assessed by open circuit potential (OCP) and potentiodynamic polarization curves and the mechanical behavior by wear resistance. Results showed that all sterilization processes caused significant morphological changes in the hybrid coating. The autoclaved sample presented the highest structural chemical changes, and, consequently, the highest degradability, even though it had a superior bioactive behavior in relation to the other samples. In addition, the sterilization processes influenced the electrochemical behavior of the hybrid coating and altered the mechanical resistance to abrasion, thus presenting lower wear performance in relation to the nonsterilized sample. [ABSTRACT FROM AUTHOR]

Some studies have related damages in duplex stainless steel (DSS) structures due to stress corrosion cracking (SCC), however, different mechanisms are observed depending of the electrolyte, temperature, electrochemical potential and steel composition. Wherefore, the SCC mechanisms of the AISI 318 DSS in a 115 000 ppm of chloride solution at 25 and 70°C were investigated. The results showed that the SCC cracks propagated in both phases, ferrite and austenite. A reduction in elongation was observed at anodic potentials caused by electrochemical dissolution and at cathodic potentials below −650 mVECS at 70°C and −750 mVECS at 25°C related to SCC mechanism. Accordingly, the more susceptible and protective potentials were determined for DSS in both temperatures. [ABSTRACT FROM AUTHOR]

The modified SAE 10B22 steel has high hardenability, which provides its use in special engineering applications, such as in self-drilling screws, with carbonitrided layer, quenched and tempered. However, these components are susceptible to hydrogen embrittlement, which can cause damage to structural components. In addition, the study of the behavior regarding to hydrogen embrittlement of components with carbonitrided layer has not been done hitherto. In this work the tempering temperature influence on hydrogen embrittlement of modified SAE 10B22 steel, was evaluated after a carbonitriding process. Standard samples and M4 × 50 screws were tested. A galvanostatic circuit was used for hydrogen charging of the samples, which were characterized by low-strain tensile test and the samples fracture were analyzed by SEM. The obtained results demonstrate that by lowering tempering temperatures, the hydrogen-loaded samples presented a greater loss of mechanical properties and greater changes of the micromechanics of fracture. In addition, the geometry of the screw was more prone to the deleterious effects of the hydrogen charging than the conventional specimens. [ABSTRACT FROM AUTHOR]

The API 5CT P110 steel is employed in oil and gas industry due to its excellent mechanical properties. However, its poor corrosion resistance makes necessary the employment of a protection. Although nickel-based and cobalt-based coatings obtained by HVOF have been widely studied regarding corrosion resistance, they are normally associated with other elements. Pure nickel and/or pure cobalt HVOF-obtained coatings have not yet been studied. Therefore, in this work, the corrosion resistance of nickel and cobalt coatings obtained by high-velocity oxy-fuel thermal spraying on API 5CT P110 steel was evaluated. The coatings were characterized regarding morphology and structure by SEM, EDS, XRD, roughness, and Vickers microhardness. The corrosion resistance was evaluated by OCP monitoring and potentiodynamic polarization in a 3.5 wt% sodium chloride solution. The results showed that both coatings acted as a barrier and avoided the contact between the steel substrate and the electrolyte due to the low melting point of the metals employed, which resulted in effective fusion of the particles. Besides, the nickel coating, promoted a better corrosion resistance compared to cobalt coating. [ABSTRACT FROM AUTHOR]

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This work aimed to study the corrosion behavior of AA2024-T3 aluminum alloy substrates pre-treated with 3 glicidoxypropyltrimethoxysilane (GPTMS) silane layers doped with different cerium ion concentrations. The withdrawal speed of substrates from the sol was 20 cm · min−1. The hybrid films were obtained by dip-coating process and analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy, Rutherford scattering spectroscopy (RBS), salt spray test, and electrochemical analyses. The correlation among the results obtained from different analyses was very good and indicated that the addition of Ce ion in the hybrid coating contributed to the corrosion resistance; however, for the high Ce ion concentration, the barrier effect of the hybrid films was deteriorated. The results obtained by RBS showed that the concentration of Ce ion in the hybrid film increased linearly with the concentration of Ce ion in the sol. Moreover, it was verified that, for the nominal concentration of 0.05 M Ce ion in the sol, the Ce atomic fraction increased in the hybrid film, while the Si atomic fraction reduced, indicating the possible modification on the silane network due to the incorporation of Ce ions. [ABSTRACT FROM AUTHOR]

This work is a corrosion study of an AISI 316L austenitic stainless steel after different plasma ion nitriding conditions. The properties of the coated AISI 316L were measured. The corrosion resistance was evaluated by cyclic voltammetry and salt spray testing. Sample surfaces were characterised by SEM and the phase determination with XRD analysis. Nanohardness was determined by using a Vickers indenter. The nitrided samples treated at 400°C, in a gaseous mixture of 5%N2 and 95%H2 for 4 and 5 h, had the best corrosion resistance. For the salt spray test, where the potential range is near the equilibrium potential, the nitrided material presented a reduced corrosion resistance. Through the control of the process parameters it is possible to improve the stainless steel surface hardness, combined with a good corrosion resistance. The highest value of temperature and N2 proportion increased the surface roughness and hardness, though it caused a decrease in corrosion resistance. [ABSTRACT FROM AUTHOR]