1. Corrosion behaviour of injection- and compression-moulded Nd–Fe–B and Sm–Fe–N magnets with different polymer bindersNikolina Lešić, Nataša Kovačević, Ingrid Milošev, 2026, original scientific article Abstract: The corrosion behaviour and environmental durability of injection- and compression-moulded Nd–Fe–B and Sm–Fe–N magnets were investigated. For injection-moulded magnets, the effects of magnetic powder type (Nd–Fe–B and Sm–Fe–N), magnetic powder particle size (100 µm and 400 µm), and polymer binder (PPS and PA12) on corrosion resistance were studied. For compression-moulded magnets with an epoxy binder, the effects of powder type and size were examined. Corrosion resistance was investigated using potentiodynamic polarisation in electrolytes of varying pH (1.8–12.8). The Sm–Fe–N magnets exhibited slightly better corrosion resistance than the Nd–Fe–B magnets, irrespective of the polymer binder. The finer magnetic powders (100 µm) showed lower corrosion resistance due to their larger specific surface area, with a more pronounced effect in the compression-moulded magnets. The type of polymer binder had only a minor effect. The hygrothermal corrosion resistance and thermal stability were evaluated using bulk corrosion (BCT) and thermal shock tests, respectively. Surface corrosion was observed in all magnets after the BCT, with the compression-moulded magnets exhibiting a greater irreversible loss of magnetic properties. The thermal shock test caused a temporary reduction in magnetic properties, with recovery after remagnetisation, demonstrating the good thermal stability of both magnet types.
Keywords: magnetic powder, injection moulding, compression moulding, polymer-bonded magnets, bulk-corrosion test, thermal shock test, polymer binders
Published in DiRROS: 04.05.2026; Views: 283; Downloads: 202
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2. Influence of conversion time on polymeric speciation in zirconium conversion coatings deposited on aluminium alloy 5754 : a ToF-SIMS studyAna Kraš, Ingrid Milošev, Antoine Seyeux, Philippe Marcus, 2026, original scientific article Abstract: The influence of conversion time on polymeric speciation and protective performance of zirconium conversion coatings (ZrCCs) on aluminium alloy AA5754 was investigated using samples treated in 150 ppm H2ZrF6 at pH 4.6 for 230 s and 480 s. Characterisation combined time-of-flight secondary ion mass spectrometry (ToF-SIMS) with region-of-interest analysis, electrochemical impedance spectroscopy in dilute Harrison’s solution after one hour, atomic force microscopy, and contact-angle measurements. ZrCC thickening is conversion-time-dependent, with a preference for growth above intermetallic particles. ToF-SIMS identified monomeric, dimeric, and trimeric zirconium hydroxide fragments, while tetrameric species were detected only at very low intensities, in contrast to previous observations on steel, possibly due to the lower overall pH increase during ZrCC formation. Despite the thicker layer obtained at 480 s, EIS indicated no improvement in corrosion protection compared with the 230 s. Morphological and wettability analyses further showed that the shorter treatment produced a rougher but more compact and uniform coating, which correlates with better short-term protective behaviour. These findings emphasise that compactness and uniformity, rather than thickness or wettability, govern the early protective function of ZrCCs and raise the question of whether tetrameric polymeric forms are required to establish a protective layer, as hypothesised for cold-rolled steel.
Keywords: polymeric speciation, zirconium conversion coatings
Published in DiRROS: 08.04.2026; Views: 245; Downloads: 159
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3. Review of coatings used for corrosion protection of aluminium alloysIngrid Milošev, Ana Koblar, 2026, review article Abstract: Aluminium and aluminium alloys are major technological metals, offering desirable mechanical properties, low density, thermal and electrical conductivity. Importantly, they exhibit high recyclability. While these materials are relatively stable and corrosion-resistant in most environments, they are often subjected to corrosion and wear in harsh environments. Coatings are the most common method of corrosion protection of aluminium and its alloys. Coatings can improve not only corrosion resistance but also wear resistance, and can add functional properties to the surface. In the present review, the coatings are summarised in five groups: (1) barrier aluminium oxide coatings, including anodised coatings, plasma electrolytic oxidised coatings, coatings deposited by atomic layer deposition, and by hydrothermal treatment, (2) conversion coatings including zirconium, chromate, titanium, trivalent chromium, and phosphate (3) metallic coatings comprising clad and electroplated metal coatings, (4) organic coatings comprising powder and liquids organic coatings, and sol–gel coatings, and (5) inhibition and wettability control coatings, comprising coatings incorporating inhibitors or nanoparticles and superhydrophobic coatings. The review focuses on production methodologies and the physical-chem-ical characteristics of coatings. Advantages and potential shortcomings of individual coatings are discussed in terms of their use and corrosion protection.
Published in DiRROS: 24.03.2026; Views: 385; Downloads: 254
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4. Influence of surface pretreatments on composition, structure and corrosion performance of zirconium conversion coating applied to AA7075-T6Gavrilo Šekularac, Janez Kovač, Ingrid Milošev, 2025, original scientific article Abstract: The effect of chemical pretreatment of aluminium alloy 7075-T6 on the composition, morphology, and structure of zirconium conversion coatings (ZrCC) was investigated. Chemical pretreatments included: (i) alkaline etching and desmutting using commercial reagents, (ii) alkaline etching using sodium hydroxide, (iii) acidic etching using nitric acid, (iv) desmutting using a commercial reagent and boiling in deionised water, and (v) alkaline etching and desmutting using nitric acid. ZrCCs were deposited at room temperature from a 200 ppm H2ZrF6 solution of pH 4.8. A commercial SurTec® coating containing zirconium and trivalent chromium was used as a benchmark. The electrochemical behaviour was evaluated using potentiodynamic polarisation measurements and electrochemical impedance spectroscopy conducted over a minimum of 5 days and up to 15 days in 0.1 M NaCl. Corrosion resistance was further assessed through immersion testing. Microstructural characterisation was performed using scanning electron microscopy with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. The SurTec® pretreatment of AA7075-T6 activated the self-sealing of the subsequently deposited ZrCC, about 40 nm thick, which exhibited the highest degree of compactness and uniformity. This study showed a significant impact of surface chemical pretreatment on the microstructural and protective properties of ZrCCs deposited on 7075 alloy.
Keywords: surface pretreatment, etching, desmutting
Published in DiRROS: 18.11.2025; Views: 637; Downloads: 347
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5. DED-LB manufactured Ti–6Al–4V–4Cu alloy : materials development, characterization, and in vivo biocompatibilityAndrej Jeromen, Anish Nair, Peter Rodič, Denis Sačer, Barbara Kapun, Maša Čater, Ana Brunčić, Katarina Kozlica, Radmila Milačič Ščančar, Andrej Cör, Edvard Govekar, Ingrid Milošev, Simon Horvat, 2025, original scientific article Keywords: Ti–6Al–4V–4Cu alloy, additive manufacturing, laser-based directed energy deposition (DED-LB), microstructure and phase analyses, corrosion, in vivo biocompatibility
Published in DiRROS: 10.11.2025; Views: 565; Downloads: 417
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7. The importance of chemical transformations of adsorbed molecules for corrosion inhibition : mercaptobenzimidazoles on copperAnton Kokalj, Erik Gregori, Barbara Kapun, Ingrid Milošev, 2025, original scientific article Abstract: This study investigates whether mercaptobenzimidazoles act as thiolates in inhibiting copper corrosion. To this end, we examined three mercaptobenzimidazole derivatives — 2-mercaptobenzimidazole (SH-BimH), 2-mercapto-1-methylbenzimidazole (SH-BimMe), and 2-(methylthio)benzimidazole (Me-S-BimH) — as corrosion inhibitors for copper in 3 wt% NaCl solution using a combined experimental and computational approach. Me-S-BimH has a thiol group (single bondSH) replaced by a methylthio group (single bondSCH ), which should prevent the formation of surface thiolates. In contrast, SH-BimMe has the same molecular formula as Me-S-BimH, but its methyl group does not cap the thiol group. Corrosion experiments reveal that after 1 h of immersion, Me-S-BimH is considerably less effective than SH-BimH and SH-BimMe at inhibiting copper corrosion. However, after 100 h of immersion, Me-S-BimH performs comparably to SH-BimH and SH-BimMe. This delayed effectiveness suggests that a molecular transformation activates Me-S-BimH over time. To explore this phenomenon, we performed a detailed DFT study of potential chemical transformations of adsorbed Me-S-BimH. Most transformations are exothermic, but only molecular deprotonation and Csingle bondS bond cleavage between the azole ring and the methylthio group exhibit sufficiently low activation barriers to occur at room temperature. Similar deprotonation and Csingle bondS bond cleavage reactions occur also for SH-BimH and SH-BimMe, leading to more strongly bound species than their intact molecular forms. Due to these transformations, Me-S-BimH and SH-BimH eventually result in the same strongly bound species, while SH-BimMe forms an analogous species. These findings may explain why, over time, all three compounds exhibit similar corrosion inhibition characteristics, and highlight the importance of chemical transformations of adsorbed molecules in corrosion inhibition.
Keywords: copper, corrosion inhibition, electrochemical measurements
Published in DiRROS: 25.08.2025; Views: 779; Downloads: 466
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8. Alumina and hafnia thin films deposited by atomic layer deposition at different temperatures on biomedical stainless steel and titaniumIvan Spajić, Sandra Drev, Urška Trstenjak, Ingrid Milošev, 2025, original scientific article Abstract: Alumina and hafnia films produced by the atomic layer deposition were applied to commercially pure Ti and stainless steel 316L specimens for protection under simulated human body conditions. The ALD films were deposited at 180 °C and 260 °C to determine how the deposition temperature affect the films' protective properties. Surface analysis of the ALD films included scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The barrier properties were tested electrochemically using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) techniques in a simulated body solution at 37 °C. Alumina thin films showed substantial barrier properties, but after 30 days of immersion, the alumina dissolved regardless of the deposition temperature. EIS tests themselves promoted the dissolution of alumina. In contrast, the barrier properties of hafnia depended significantly on deposition temperature. Hafnia deposited at 180 °C exhibited substantial protective properties and remarkable stability over an extended immersion period. However, when deposited at 260 °C hafnia films showed strong protection at the outset, but after a few days of immersion, they lost their protective ability due to porosity. The key factors affecting the barrier properties of ALD hafnia films were the proportion of the crystalline phase and how crystallites formed.
Keywords: thin films, atomic layer deposition, titanium alloys, biomedical steel, medical implants
Published in DiRROS: 15.07.2025; Views: 1125; Downloads: 684
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9. Corrosion of sintered NdFeB permanent magnetsTerezija Poženel Kovačič, Nataša Kovačević, Ingrid Milošev, 2025, review article Abstract: The green transition to reduce reliance on fossil fuel energy sources and minimise global warming is accelerating the need for NdFeB permanent magnet materials. Sintered NdFeB magnets cover the largest segment percentage within the permanent magnet type group, with a share of over 50%. The microstructure of NdFeB magnets includes grains of the Nd1+εFe4B4 (B-rich phase), which form grain boundaries with both the Nd-rich (Nd4Fe) and matrix (Nd2Fe14B) phases. NdFeB magnets are prone to degradation in harsh environments due to the low corrosion resistance of both iron and neodymium. Consequently, magnets require corrosion protection because their magnetic properties would be jeopardised due to the degradation caused by the corrosion process. Understanding magnets’ electrochemical and corrosion properties is crucial for developing their corrosion protection and thus prolonging their smooth operation in numerous industrial applications. This review aims to present the fundamental corrosion processes on sintered NdFeB magnets, provide an overview of the contemporary magnet production processes of NdFeB magnets and their impact on the corrosion resistance, and summarise the corrosion protection of NdFeB magnets. Prospects are presented, especially regarding the use of magnets in the transportation (hybrid and electric vehicles) industry and the development of alternative types of coatings.
Keywords: sintered magnets, green transition
Published in DiRROS: 03.07.2025; Views: 1244; Downloads: 471
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10. Zr and Zr-Cr commercial conversion coatings deposited on 3003 aluminium alloy foilMaja Mujdrica Kim, Barbara Kapun, Ingrid Milošev, 2025, original scientific article Abstract: MAVOMcoat MC1300 (Zr-Cr-based coating) and MC1700 (Zr-based coating) on chemically pre-treated aluminium alloy 3003. Conversion times varied from 80 s to 45 min. After deposition, the samples were subjected to three post-treatments: air drying for 15 min, air drying for 24 h, and immersion in 3.5 wt% NaCl solution for 24 h. Corrosion resistance was evaluated using electrochemical measurements, whereas scanning electron microscopy with energy dispersive spectroscopy and X-ray photoelec tron spectroscopy were employed for surface analysis. Based on the evaluation of corrosion parameters, the optimal conversion times for MC1700 and MC1300 were determined to be 10 min and 7 min, respectively. The conversion coatings MC1700 and MC1300 were characterised by distinct elemental compositions, with the former predominantly comprising Zr, O, Al and F, and the latter Zr, O, Al, Cr and F. Notably, the thickness of coatings was between 10 and 170 nm, depending on the type of coating and location (matrix or intermetallic particles). The 24-hour immersion of MC1700 ZrCC in 3.5 wt% NaCl led to progressive build-up of Zr oxide and release of fluoride from the coating.
Published in DiRROS: 10.06.2025; Views: 1147; Downloads: 324
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