Materials and Corrosion-werkstoffe Und Korrosion最新文献

In this study, Hydroxyapatite (HA) modified HA-Ti composite coatings were applied to the surface of the Ti-6Al-4V (Ti64) alloy, which is crucial for biomedical applications, using the TIG cladding method. HA fraction caused a notable decrease in adhesion strength and ductility; however, the 5% HA composition maintained mechanical integrity while providing biological advantages. Surface contact angle measurements showed that HA addition made the surfaces more hydrophilic, with the lowest contact angle (~58°) observed in the 10%HA coating, which suggests improved interaction with biological fluids, cell adhesion, and protein adsorption. Electrochemical test results indicated that the 10% HA coatings exhibited the highest corrosion resistance and the most stable oxide film behavior. In immersion tests conducted in simulated body fluid (SBF), significant Ca-P deposition was observed on the 10% HA surfaces, supporting their high bioactivity potential. Overall, the results demonstrate that HA-reinforced Ti composite coatings produced through TIG welding are highly promising candidates for surface modification of biomedical implants, offering both structural and biological functionality.

In this study, the corrosion-fatigue behavior of 316L steel under various loading frequencies in molten nitrate salt at 565°C were conducted. The results indicate that the fatigue life of 316L steel was similar in air and molten salt environments at a low frequency (0.019 Hz). However, at the relatively higher loading frequencies (0.038, 0.076, and 0.152 Hz), a reduction in fatigue life was observed compared with that in air. Fatigue loading significantly accelerated the corrosion of 316L steel, and the extent of acceleration was dependent on the loading conditions. At 0.019 Hz, the cracking of the oxide layer in molten nitrate salts was limited due to the relatively low strain rate, whereas at 0.038, 0.076, and 0.152 Hz, it became considerably more severe. At higher loading frequencies (≥ 0.038 Hz), significant cracking of the oxide layer not only creates pathways for molten salt to corrode crack tips further, but also promotes multi-site fatigue crack initiation.

The aim of this study is to assess the role of red mud addition to alkali-activated materials (AAMs) on the corrosion resistance of steel in mortars. Microstructural properties, including total porosity and pore structure, are determined using (MIP). Resistance to chloride penetration is tested using accelerated chloride penetration (NT BUILD 443) and chloride migration (NT BUILD 492) test. Corrosion properties are evaluated by measuring corrosion potential, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) using two types of corrosion cell set up. In both cell set ups, steels embedded in alkali-activated mortars with red mud exhibited better corrosion resistance than steels in alkali-activated mortars without red mud. It is confirmed that the addition of red mud in AAMs contributes to pore refinement and chloride binding in the case of the slag-based system and to the improvement of the properties of the passive film in the case of both the slag-based and fly ash-based systems.

Stray currents significantly affect microbial metabolism and pipeline corrosion. This study explored the corrosion of X70 steel in near-neutral solution under direct current (DC) and sulfate-reducing bacteria (SRB). The corrosion rate was determined with the electrochemical technique and the corrosion morphology and corrosion products were respectively characterized by SEM and XPS. Results showed minimal uniform corrosion was observed in sterile solution without DC, but pitting corrosion occurred in bacterial solution. Without SRB, DC caused extensive corrosion, and the corrosion rate first dropped, then rose with increasing DC density, hitting a minimum at 0.5 mA/cm². When DC and SRB acted together, the corrosion rate was higher than with DC alone, followed a similar trend, and correlated with SRB activity. At 0.1–0.5 mA/cm² DC, SRB activity increased and dominated corrosion, causing pitting. However, at 1 mA/cm² DC, SRB was suppressed and DC took over, and severe pitting was observed. In sterile solution, DC facilitated the formation of protective Fe₂O₃ and Fe₃O₄ layers. Conversely, in bacterial solutions, the corrosion product FeS inhibited the oxidation of Fe²⁺ by DC.

This paper investigates the morphological characteristics of the corrosion-induced cracks in reinforced concrete of the rail infrastructures induced by stray current and chloride ions. Cracks and the internal structure were obtained by X-ray computed tomography. The spatial morphology was classified into Major Cracks, Secondary Cracks, and Internal Cracks. The width tendency, vertical penetration depth, and spatial morphology of the cracks can reflect the pattern and sequence of crack extension. The radial depths of the cracks in the same specimen decrease sequentially. When the defects are dispersed around the steel bar, the cracks correspond to a smaller average radial depth. The tortuosity of the crack reflects the length of the crack, the rate of the width variation, the relative position of the defects in relation to the aggregate as the crack expands, and the effect of the defects and aggregate on the crack extension. The results characterize the spatial morphology of corrosion-induced cracks, which are helpful for further research on the extension pattern of corrosion-induced cracks and nonuniform corrosion of steel bars.