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Objective: The aim of this study is to fi nd out how many patients with an ongoing smell and taste disorder after COVID-19 infection, can improve the subjective perception of smell by olfactory training method. Methods: Patients after COVID-19 (fi rst and second wave of the pandemic in 2020 and 2021) with persisting smell disorder (hyposmia, anosmia, parosmia, fantosmia) with or without taste disorder and while the olfactory disorder did not improve within one month afterrecovery, signed up on the website www.cuch.sk and asked for a testing set (perfumed felt-tip pens) to be sent. After a self-examination at home, each respondent fi lled out an on-line questionnaire and sent it to the Neurobio logical Institute of the BMC SAV. Patient with confi rmed hypo and anosmia underwent an ENT examination at contracted ENT workplaces in Slovakia. All the 117 patients included got through the olfactory training, twice a day, following the instructions. The control examination was performed after three and six months of smell training. Smell and taste status was evaluated by visual analogue scale (VAS) from 1 to 10 in admission and discharge of the study. According to VAS, the average entering olfactory status was 4 and the average taste status reached an average of 2. At admission, 28 patients entering the study suff ered from parosmia, 18 from phantosmia, and 20 from dysgeusia. Results: After the olfactory training, improvement of smell capability was observed in 96 patients, which is 73% from the whole group of patiets (117) with hyposmia and anosmia. The discharge olfactory score after 6 months of olfactory training reached grade 8 according to VAS. Improvement of taste capability was observed in 47 patients, which is 65% from the whole group of patients (72) with hypogeusia and dysgeusia. The discharge taste score after six months of olfacory training reached grade 4 according to VAS. However, various forms of dysgeusia, parosmia, or phantosmia persisted after the olfactory training in 18 patients. Conclusion: Smell (olfactory) training is currently considered the most eff ective rehabilitation method for improving impaired olfactory function after COVID-19 infection. Better subjective results were observed in the restitution of quantitative smell disorder than in quantitative taste disorder. Key words anosmia – hyposmia – COVID-19 – parosmia – phantosmia – hypogeusia – dysgeusia – olfactory training

Objective: We present a case report of a congenital malformation of the uropoetic tract in one of the monoamniotic twins. Case report: A 24-year-old primigravida with male monochorionic monoamniotic twins was dia gnosed with congenital malformation in fetus A at 24 weeks of gestation. Ultrasound verified macrocystic dysplasia and contralateral renal agenesis. Planned caesarean section was performed after the observational management of the patient in the 34th gestational week. In fetus B, a physiological finding was confirmed on the postpartum ultrasonography. In fetus A, CT examination of the abdomen confirmed the finding of left kidney agenesis and polycystic degeneration of the right kidney. Exitus letalis was stated on the newborn's 5th day. Conclusion: The occurrence of the described combination of congenital malformation in monoamniotic twins is rare. When dysplasia significantly affects the function of the parenchyma, renal agenesis with multicystic dysplasia of the other kidney is a condition incompatible with life. For the intrauterine survival of the affected fetus, the normal renal function of the twin was important and thus the normal volume of amniotic fluid was maintained. As a result, the fetus did not develop extrarenal symptoms of the Potter sequence in the described case – especially pulmonary hypoplasia and the newborn was able to ventilate spontaneously. The death was caused by the consequences of renal failure associated with anuria. Key words: monoamniotic twins – macrocystic renal dysplasia – renal agenesis

Tail-anchored (TA) membrane proteins, accounting for roughly 2% of proteomes, are primarily targeted posttranslationally to the endoplasmic reticulum membrane by the guided entry of TA proteins (GET) pathway. For this complicated process, it remains unknown how the central targeting factor Get3 uses nucleotide to facilitate large conformational changes to recognize then bind clients while also preventing exposure of hydrophobic surfaces. Here, we identify the GET pathway in Giardia intestinalis and present the structure of the Get3–client complex in the critical postnucleotide-hydrolysis state, demonstrating that Get3 reorganizes the client-binding domain (CBD) to accommodate and shield the client transmembrane helix. Four additional structures of GiGet3, spanning the nucleotide-free (apo) open to closed transition and the ATP-bound state, reveal the details of nucleotide stabilization and occluded CBD. This work resolves key conundrums and allows for a complete model of the dramatic conformational landscape of Get3.

An Fe-based coating was thermally sprayed onto the surface of AZ91 magnesium alloy via the High-Velocity-Oxygen-Fuel (HVOF) method. The thermally sprayed coating with a thickness of 530 ± 25 µm and a porosity of 0.7 ± 0.1% did not show any macrostructural defects and did not cause any degradation of the AZ91 alloy. Laser remelting of the surface layer of the sprayed coating resulted in the recrystallization of the structure and the disappearance of presented pores, splat boundaries, and other defects. This led to an increase in the hardness of the remelted layer from the original 535 ± 20 HV0.3 up to 625 ± 5 HV0.3. However, during the laser remelting at a laser power of 1000 W, stress cracking in the coating occurred. The tribological properties were evaluated by the ball-on-plate method under dry conditions. Compared to the uncoated AZ91 magnesium alloy, a higher value of friction coefficient (COF) was measured for the as-sprayed coating. However, there was a decrease in wear rate and weight loss. The remelting of the surface layer of the as-sprayed coating led to a further decrease in the wear rate and weight loss. Based on the obtained data, it has been shown that the application of laser-remelted thermally sprayed Fe-based coatings on AZ91 Mg alloy improves hardness and tribological properties compared to bare Mg alloy and as-sprayed Fe-based coatings.

Mitochondrial metabolism is entirely dependent on the biosynthesis of the [4Fe-4S] clusters, which are part of the subunits of the respiratory chain. The mitochondrial late ISC pathway mediates the formation of these clusters from simpler [2Fe-2S] molecules and transfers them to client proteins. Here, we characterized the late ISC pathway in one of the simplest mitochondria, mitosomes, of the anaerobic protist Giardia intestinalis that lost the respiratory chain and other hallmarks of mitochondria. Identification of the late ISC interactome revealed unexpected involvement of the aerobic marker protein BolA and specific interaction of IscA with the outer mitosomal membrane. Although we confirmed that the synthesis of the Fe-S cluster remained the only metabolic role of mitosomes, we also showed that mitosomes lack client proteins that require the [4Fe-4S] cluster. Instead, by knocking out the bolA gene from the G. intestinalis genome, we showed that, unlike aerobic mitochondria, the late ISC mitosomal pathway is involved in the assembly of cytosolic [4Fe-4S] clusters. Thus, this work reveals an unexpected link between the formation of mitochondrial and cytosolic [4Fe- 4S] clusters. This may either be a consequence of mitochondrial adaptation to life without oxygen, or it represents a general metabolic coupling that has not been previously observed in the complex mitochondrial metabolism of aerobes.

Tail-anchored (TA) membrane proteins, accounting for roughly 2% of proteomes, are primarily targeted posttranslationally to the endoplasmic reticulum membrane by the guided entry of TA proteins (GET) pathway. For this complicated process, it remains unknown how the central targeting factor Get3 uses nucleotide to facilitate large conformational changes to recognize then bind clients while also preventing exposure of hydrophobic surfaces. Here, we identify the GET pathway in Giardia intestinalis and present the structure of the Get3-client complex in the critical postnucleotide-hydrolysis state, demonstrating that Get3 reorganizes the client-binding domain (CBD) to accommodate and shield the client transmembrane helix. Four additional structures of GiGet3, spanning the nucleotide-free (apo) open to closed transition and the ATP-bound state, reveal the details of nucleotide stabilization and occluded CBD. This work resolves key conundrums and allows for a complete model of the dramatic conformational landscape of Get3.

Formation of mitochondria by the conversion of a bacterial endosymbiont was a key moment in the evolution of eukaryotes. It was made possible by outsourcing the endosymbiont’s genetic control to the host nucleus, while developing the import machinery for proteins synthesized on cytosolic ribosomes. The original protein export machines of the nascent organelle remained to be repurposed or were completely abandoned. This review follows the evolutionary fates of three prokaryotic inner membrane translocases Sec, Tat, and YidC. Homologs of all three translocases can still be found in current mitochondria, but with different importance for mitochondrial function. Although the mitochondrial YidC homolog, Oxa1, became an omnipresent independent insertase, the other two remained only sporadically present in mitochondria. Only a single substrate is known for the mitochondrial Tat and no function has yet been assigned for the mitochondrial Sec. Finally, this review compares these ancestral mitochondrial proteins with their paralogs operating in the plastids and the endomembrane system.

Pure Mg samples were prepared by powder metallurgy using the cold and hot compacting methods. Cold compacted pure Mg (500 MPa/RT) was characterized by 5% porosity and the mechanical bonding of powder particles. Hot compacted samples (100 MPa/400 °C and 500 MPa/400 °C) exhibited porosity below 0.5%, and diffusion bonding combined with mechanical bonding played a role in material compaction. The prepared pure Mg samples and wrought pure Mg were subjected to corrosion tests using electrochemical impedance spectroscopy. Similar material corrosion behavior was observed for the samples compacted at 500 MPa/RT and 100 MPa/400 °C, however, hot compacted samples processed at 500 MPa/400 °C exhibited longer corrosion resistance in 0.9% NaCl solution. The difference in corrosion behavior was mainly related to the different binding mechanisms of the powder particles. Cold compacted samples were characterized by a more pronounced corrosion attack and the creation of a porous layer of corrosion products. Hot compacted samples prepared at 500 MPa/400 °C were characterized by uniform corrosion and the absence of a layer of corrosion products on the specimen surface. Powder-based cold compacted samples exhibited lower corrosion resistance compared to the wrought pure Mg, while the corrosion behavior of the hot compacted samples prepared at 500 MPa/400 °C was similar to that of wrought material.

The presence of Al-Si coating on 22MnB5 leads to the formation of large ferritic bands in the dominantly martensitic microstructure of butt laser welds. Rapid cooling of laser weld metal is responsible for insufficient diffusion of coating elements into the steel and incomplete homogenization of weld fusion zone. The Al-rich regions promote the formation of ferritic solid solution. Soft ferritic bands cause weld joint weakening. Laser welds reached only 64% of base metal’s ultimate tensile strength, and they always fractured in the fusion zone during the tensile tests. We implemented hybrid laser-TIG welding technology to reduce weld cooling rate by the addition of heat of the arc. The effect of arc current on weld microstructure and mechanical properties was investigated. Thanks to the slower cooling, the large ferritic bands were eliminated. The hybrid welds reached greater ultimate tensile strength compared to laser welds. The location of the fracture moved from the fusion zone to a tempered heat-affected zone characterized by a drop in microhardness. The minimum of microhardness was independent of heat input in this region.

Aim: Pressure ulcers represent a major postoperative complication. We retrospectively analyse data and identify risk factors for the development of pressure ulcers in patients undergoing surgery at the 1st Surgical Clinic of St. Anne’s Hospital in Brno between 2017 and 2018. Methods: We used data from the hospital’s information system and a purpose-built electronic database (I-hojeni.cz). Statistical analysis was performed using Pearson‘s chi-square at a significance level of 0.05, the variables used included: age, Body Mass Index (BMI), number and grade of pressure ulcers and comorbidities (history of cardiovascular diseases, diabetes mellitus, chronic renal failure, neurological and oncological diseases). Results: 5,851 inpatients underwent surgery (91.15% of the total of 6,419) between 2017 and 2018. Pressure ulcers newly developed in 86 patients (1.46%), 40 men and 46 women. The patients’ average age was 79.85, age was confirmed as a predictive factor for pressure ulcer formation. The average BMI value was 24.13, the relationship between BMI and development of pressure ulcers was not statistically significant. The average pressure ulcer grade was 2.04 and the average number per patient 1.5. Pressure ulcers mostly developed on the heels, buttocks and sacrum. On average the period between a patient’s admission and operation was 2.79 days (0–16 days), it did not prove to be a factor. 56 patients (65.11%) had a history of neurological disorder – a predictive factor – the correlation was not statistically significant, similarly to oncological diseases 30 (24.41%), 19 patients (22.09%) with pressure ulcers died. Conclusion: Our study is unique in expanding our understanding of multiple risk factors for the development of pressure ulcers, it suggests that age and a history of neurological disorder in particular are key risk factors while other risk factors generally considered to be significant (mobility, nutritional factors) did not prove so.

The present study is focused on the structural phase transition in (La,Ce)Pd2Al2−xGax investigated by low temperature X-ray powder diffraction. All parent compounds crystallize in the tetragonal CaBe2Ge2 structure type (P4/nmm, 129) at room temperature and undergo structural phase transitions at low temperatures. Rietveld analysis of the measured patterns shows that the low temperature structures of (La,Ce)Pd2Al2 and (La,Ce)Pd2Ga2 have the same space groups and Wyckoff positions, but exhibit different magnitude of distortion and different characteristics of the structural transition. A small continuously appearing distortion is present in the Al parent compounds while the Ga ones exhibit a large discontinuously appearing distortion. These low temperature structures can be described using the C m m e , 67 space group which is translationengleiche subgroup of the tetragonal P 4 / n m m , 129 space group. The concentration dependence of the temperature where the distortion occurs has a minimum or is almost suppressed at a concentration of x ∼ 0.4 (cerium series) and x ∼ 1.6 (lanthanum series). To support our experimental findings we also present density function theory calculations which confirm the structural stability as experimentally observed. We discuss the impact of structural properties in the studied series on the previously observed development of physical properties such as superconductivity and magnetic excitations in neutron scattering spectra.

Fluoride conversion coating was applied on wrought AZ61 magnesium alloy by the immersion of alloy in Na[BF4] molten salt. Two different temperatures 430 °C and 450 °C, and different treatment times of 0.5; 2 and 8 h were used for the coating preparation. The surface morphology and the cross-sections of the coatings were investigated by scanning electron microscopy, focused ion beam cutting and energy-dispersive X-ray spectroscopy. The electrochemical corrosion characteristics of coated material varied with processing conditions. A significant improvement of electrochemical corrosion properties of the AZ61 magnesium alloy coated with fluoride conversion coatings was revealed by the potentiodynamic tests and electrochemical impedance spectroscopy.

Wrought AZ31 magnesium alloy was used as the experimental material for fluoride conversion coating preparation in Na[BF4] molten salt. Two coating temperatures, 430 °C and 450 °C, and three coating times, 0.5, 2, and 8 h, were used for the coating preparation. A scanning electron microscope and energy-dispersive X-ray spectroscopy were used for an investigation of the surface morphology and the cross-sections of the prepared coatings including chemical composition determination. The corrosion resistance of the prepared specimens was investigated in terms of the potentiodynamic tests, electrochemical impedance spectroscopy and immersion tests in the environment of simulated body fluids at 37 ± 2 °C. The increase in the coating temperature and coating time resulted in higher coatings thicknesses and better corrosion resistance. Higher coating temperature was accompanied by smaller defects uniformly distributed on the coating surface. The defects were most probably created due to the reaction of the AlxMny intermetallic phase with Na[BF4] molten salt and/or with the product of its decomposition, BF3 compound, resulting in the creation of soluble Na3[AlF6] and AlF3 compounds, which were removed from the coating during the removal of the secondary Na[MgF3] layer. The negative influence of the AlxMny intermetallic phase was correlated to the particle size and thus the size of created defects.

The type 2 secretion system (T2SS) is present in some Gram-negative eubacteria and used to secrete proteins across the outer membrane. Here we report that certain representative heteroloboseans, jakobids, malawimonads and hemimastigotes unexpectedly possess homologues of core T2SS components. We show that at least some of them are present in mitochondria, and their behaviour in biochemical assays is consistent with the presence of a mitochondrial T2SS-derived system (miT2SS). We additionally identified 23 protein families co-occurring with miT2SS in eukaryotes. Seven of these proteins could be directly linked to the core miT2SS by functional data and/or sequence features, whereas others may represent different parts of a broader functional pathway, possibly also involving the peroxisome. Its distribution in eukaryotes and phylogenetic evidence together indicate that the miT2SS-centred pathway is an ancestral eukaryotic trait. Our findings thus have direct implications for the functional properties of the early mitochondrion., Bacteria use the type 2 secretion system to secrete enzymes and toxins across the outer membrane to the environment. Here the authors analyse the T2SS pathway in three protist lineages and suggest that the early mitochondrion may have been capable of secreting proteins into the cytosol.

CRISPR/Cas9 system is an extremely powerful technique that is extensively used for various genome modifications in different organisms including parasitic protists. Giardia intestinalis, a protist parasite infecting about 280 million people around the world each year, has been eluding the routine use of CRISPR/Cas9 for generating knock-out cell lines due to the presence of four copies of each gene in its two nuclei. Apart from single exception employing rather laborious Cre/loxP system, no full knock-out cell line has been established yet. In this work, we show the ability of in-vitro assembled CRISPR/Cas9 components to successfully edit the genome of G. intestinalis. We further established a cell line stably expressing Cas9 in both G. intestinalis nuclei. Subsequent introduction of a template for homologous recombination containing the transcription units for the resistance marker and gRNA resulted in the removal of all gene copies at once for three independent experimental genes, mem, cwp1 and mlf1. The method was also applicable for the incomplete disruption of an essential gene, as documented by markedly decreased expression of tom40. Finally, testing the efficiency of Cas9-induced recombination revealed that homologous arms as short as 150 bp can be sufficient to establish a full knock-out cell line in G. intestinalis.

This paper deals with the study of the crystallization and phase transformation of Ni-P coatings deposited on AZ91 magnesium alloy. Prepared samples were characterized in terms of surface morphology and elemental composition by means of scanning electron microscopy with energy-dispersive spectroscopy analysis. The results of X-ray diffraction analysis and differential scanning calorimetry suggested that increasing the phosphorus content caused Ni-P coatings to develop an amorphous character. The crystallization of Ni was observed at 150, 250, and 300 °C for low-, medium- and high-phosphorus coatings, respectively. The Ni crystallite size increased with increasing temperature and decreasing P content. Conversely, the presence of the Ni3P phase was observed at a maximum peak of 320 °C for the high-phosphorus coating, whereas the crystallization of the Ni3P phase shifted to higher temperatures with decreasing P content. The Ni3P crystallite size increased with increasing temperature and increasing P content. An increase in microhardness due to the arrangement of Ni atoms and Ni3P precipitation was observed. The deposition of as-deposited Ni-P coatings led to an improvement in the corrosion resistance of AZ91. However, the heat treatment of coatings resulted in a deterioration in corrosion properties due to the formation of microcracks.

Evolution of magnetism in single crystals of the van der Waals compound $\mathrm{V}{\mathrm{I}}_{3}$ in external pressure up to 7.3 GPa studied by measuring magnetization and ac magnetic susceptibility is reported. Four magnetic phase transitions, at ${T}_{1}=54.5\phantom{\rule{0.16em}{0ex}}\mathrm{K}, {T}_{2}=53\phantom{\rule{0.16em}{0ex}}\mathrm{K}, {T}_{\mathrm{C}}=49.5\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and ${T}_{\mathrm{FM}}=26\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, respectively, have been observed at ambient pressure. The first two have been attributed to the onset of ferromagnetism in specific crystal-surface layers. The bulk ferromagnetism is characterized by the magnetic ordering transition at Curie temperature ${T}_{\mathrm{C}}$ and the transition between two different ferromagnetic phases ${T}_{\mathrm{FM}}$, accompanied by a structure transition from monoclinic to triclinic symmetry upon cooling. The pressure effects on magnetic parameters were studied with three independent techniques. ${T}_{\mathrm{C}}$ was found to be almost unaffected by pressures up to 0.6 GPa whereas ${T}_{\mathrm{FM}}$ increases rapidly with increasing pressure and reaches ${T}_{\mathrm{C}}$ at a triple point at \ensuremath{\approx} 0.85 GPa. At higher pressures, only one magnetic phase transition is observed moving to higher temperatures with increasing pressure to reach 99 K at 7.3 GPa. In contrast, the low-temperature bulk magnetization is significantly reduced by applying pressure (by more than 50% at 2.5 GPa) suggesting a possible pressure-induced reduction of vanadium magnetic moment. First-principles calculations of $\mathrm{V}{\mathrm{I}}_{3}$ under pressure allow us to ascribe the evolution of ${T}_{\mathrm{C}}$ with pressure to the reduction of interplanar distance, including the observed slope change at 0.6 GPa. These calculations also describe the associated band gap closing, showing that with a modest compression the material would become metallic. Overall, the large pressure range covered corresponds to a significant change of interplanar interactions. The obtained data thus allow us to shed light on how does the transition between the three-dimensional (3D) and quasi-2D system affect magnetic interactions in the system.

Magnesium-zinc based materials are characteristic with the creation of intermetallic phases, strongly influencing material mechanical properties. Mg-Zn powder mixture (10 % wt. Zn) was processed by the hot pressing method under 500 MPa at 300 °C. Microstructure of the prepared material was analyzed in terms of light optical microscopy and scanning electron microscopy. Chemical and phase composition of the processed material were analyzed by energy-dispersive X-ray spectroscopy and X-ray powder diffraction, respectively. Microhardness testing was adopted to characterize created structure mechanical properties on the microscopic level. Depending on the Mg-Zn powder mixture local chemical composition, the structural and chemical analysis of the processed material revealed that it consisted of magnesium and zinc rich areas, and MgZn2 intermetallic phase. The MgZn2 intermetallic phase belongs to the so-called Laves phases group with the general formula AB2. Laves phases are characteristic with high hardness and the related high brittleness. Their presence in the material usually results in deterioration of mechanical properties such as strength and toughness. The microhardness of magnesium and zinc rich areas in the processed material was 58±1 HV 0.025 and 47 ±1 HV 0.025, respectively, while the value of the microhardness for MgZn2 intermetallic phase was 323±12 HV 0.025. Different behavior and mechanical properties of the present phases was observed on the fracture surfaces of specimens broken during the 3-point bend test. While brittle fracture was a characteristic feature for MgZn2 intermetallic phase, the rest of the material exhibited more ductile fracture behavior with characteristic transgranular failure.

A hybrid laser-tungsten inert gas (LasTIG) welding system was applied for 3-mm-thick S460MC and S700MC high-strength low-alloy steel sheet butt welding with the aim to reduce the cooling rate compared with laser welding. The effect of the electric current was evaluated. Increasing arc current led to the increase of fused metal and heat-affected-zone (HAZ) dimensions. Fused metal grains were larger whereas the microhardness increase toward the base metal was lower at higher currents in this region. Microhardness peaks corresponding to the coarse-grained HAZ were reduced at higher currents for S460MC but were almost not affected in S700MC. The tensile strength of both the laser weld and LasTIG welds was comparable to the base metal for both alloys.

Laser welding accompanied by tungsten inert gas welding was applied for 3 mm thick high strength low alloy S460MC steel butt joining with the aim to study the effect of arc electric current on weld cooling rate and thus weld microstructure and mechanical properties. Preheating realized by the arc decreased microhardness peaks in coarse-grained heat affected zone while strength properties were not degraded. Dissimilar S460MC to DC01 mild steel welds were performed with different positions of tungsten electrode towards the laser beam trajectory to maintain uniform weld profile.

Among a large group of R2T2X intermetallics (R = rare earth, T = transition element, X = p-metal) crystallizing in the Shastry-Sutherland-like tetragonal structure, Ce2Pd2In represents a rare example of Ce-based ferromagnet, reached, however via an antiferromagnetic phase stable at higher temperatures. Here we describe the development of magnetism in Ce2Pd2In under external hydrostatic and uniaxial pressure, monitored by means of electrical resistivity, magnetization, and AC magnetic susceptibility experiments on a high-quality single crystal. The experiments prove a stability of the 4f magnetism in pressures up to 3 GPa. At these pressures only slightly reduced spontaneous magnetization in the FM state and enhanced electrical resistivity with signs of Kondo lattice behavior are observed. The AFM Neel temperature (TN = 4.65 K) is essentially pressure independent, while the Curie temperature (TC = 4.16 K at ambient pressure) significantly decreases under hydrostatic pressure. The fact that the ferromagnetic phase can be re-entered in weak magnetic fields (0.05 T) proves that the two types of magnetic order are effectively degenerate. Interestingly, TC is not affected by uniaxial pressure applied along the tetragonal c-axis, TN value exhibits only a weak decrease of 0.25 K GPa−1 under such uniaxial pressure. The crystal structure of Ce2Pd2In exhibits a strongly anisotropic thermal expansion with anomalous expansion of the c-parameter with decreasing T. Modest size of magnetostriction effects, observed by dilatometry at ambient pressure, indicates only regular magnetovolume interactions.

Field-assisted sintering is a modern approach to novel magnesium materials preparation; however, it is unclear whether it is better to sinter green compact or loose powder. This work focuses on preparing bulk materials from loose and cold-compacted magnesium powder through a field-assisted sintering technique – spark plasma sintering (SPS). Green compacts were prepared under a series of compacting pressures from 100 MPa to 500 MPa. SPS was performed at 400 °C, 500 °C, and 600 °C applying additional pressure of 100 MPa during the sintering process. Prepared materials were analysed regarding their microstructure, hardness, and microhardness and through the three-point bending test and fractography. The green compacts porosity decreased with increased cold-compaction pressure. The SPS positively affected porosity and mechanical properties only in loose powder and the lowest cold-compacted green compacts. Increasing cold compaction pressure of the green compacts above 200 MPa is therefore unfavourable for further SPS processing.

Purpose The purpose of this paper is to compare electrochemical corrosion characteristics of conventional and unconventional fluoride conversion coating prepared on magnesium alloy. Design/methodology/approach The chemical reaction of AZ61 with 38 wt.% hydrofluoric acid (HF) for 24 h was used as a conventional way of fluoride conversion coating preparation. The unconventionally prepared coating was created in Na[BF4] salt melt at 450°C for 2 h. Morphology and chemical composition of prepared fluoride conversion coatings were studied with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Electrochemical corrosion characteristics of the coatings were analyzed in Hank’s solution using potentiodynamic tests. Findings Both the coating preparation ways resulted in the creation of uniform conversion coatings with the same thickness (1.3 ± 0.1 μm). Some defects were observed on the coatings surface; however, the defects did not reach the AZ61 surface. Electrochemical tests performed in Hank’s solution at 37°C showed an improvement of corrosion resistance of AZ61 treated with fluoride conversion coatings when compared to the untreated material. Unconventionally prepared coating reached better electrochemical corrosion characteristics when compared to the conventionally prepared coating. Originality/value Electrochemical corrosion characteristics of AZ61 magnesium alloy can be improved with fluoride conversion coatings. Two methods are used in the literature for the coatings preparation. The conventional method is based on dipping of the coated material to the HF, and the unconventional method lies in dipping of the sample to the Na[BF4] salt melt. The main purpose of the present study is to analyze the conventionally and unconventionally prepared coatings in terms of chemical analysis, morphology and material corrosion protection (electrochemical corrosion characteristics), while the data are not provided in the literature, according to the authors’ knowledge. Very similar coatings were prepared using both the methods from the morphological and chemical composition point of view. However, unconventionally prepared coating created in Na[BF4] salt melt reached better electrochemical corrosion characteristics compared to the coating prepared in HF.