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Query: "author" (Miha Hren) .

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11.
Characterization of steel corrosion processes in various blended cements by means of coupled multi-electrode arrays
Miha Hren, Tadeja Kosec, Andraž Legat, 2023, original scientific article

Abstract: Supplementary cementitious materials can affect the porosity of concrete, pore solution pH and chloride binding, all of which influence the type and magnitude of corrosion damage. Advanced corrosion monitoring techniques are needed to follow the development of corrosion on steel embedded in concrete across space and over time. In this study, coupled multi-electrode arrays (CMEAs) were used to characterise corrosion processes in OPC and three blended cements. Cyclic wetting with chlorides was undertaken to initiate corrosion. The results showed three distinct types of corrosion: localised corrosion (CEM I), localised corrosion that expanded over time (CEM II), and a combination of localised and general corrosion (CEM III and CEM IV). Cathodic locations were also monitored successfully, and the corrosion behaviour was related to total porosity and pH of the pore solution. MicroCT was used to quantify the volume of corroded material, which agreed well with results calculated from the CMEA measurements.
Keywords: blended cements, coupled multi-electrode array, corrosion of steel in concrete, supplementary cementitious materials, open access
Published in DiRROS: 29.05.2023; Views: 557; Downloads: 326
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12.
Tribocorrosion susceptibility and mechanical characteristics of as-received and long-term in-vivo aged nickel-titanium and stainless-steel archwires
Jasmina Primožič, Miha Hren, Uroš Mezeg, Andraž Legat, 2022, original scientific article

Abstract: To evaluate the effect of long-term in-vivo aging on orthodontic archwires, we aimed to assess the triboelectrochemical and mechanical characteristics of as-received and in-vivo aged nickel-titanium (NiTi) and stainless-steel (SS) orthodontic archwires. Four consecutive tribocorrosion cycles on six NiTi and six SS archwires, as-received and in-vivo aged, were performed on a reciprocal tribometer. Electrochemical noise and friction coefficient measurements, three-dimensional surface profiling, and hardness measurements were performed. Repassivation times of as-received archwires were longer than of the in-vivo aged; however, were shorter for NiTi. Friction coefficients were higher for NiTi than for SS archwires. Sudden major current drops concomitant with inverse potential shifts and friction coefficients’ fluctuations, were seen for as-received (last cycle) and in-vivo aged (last three cycles) NiTi archwires. More pronounced tribocorrosion damage was observed on in-vivo aged NiTi than on other archwires. Hardness was generally higher inside the wear track of archwires. Long-term in-vivo exposure decreases the corrosion susceptibility of archwires, more evidently for the NiTi ones. Sudden major fluctuations in electrochemical current, potential, and friction coefficient detected for NiTi archwires, might be related to localized residual parts of the oxide layer persisting due to increased surface roughness or to phase transformations of the alloy’s crystal structure.
Keywords: tribocorrosion, orthodontic archwires, electrochemical noise, open access
Published in DiRROS: 26.04.2023; Views: 622; Downloads: 305
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