The investigation of the effect of pH and fly ash (FA) as a corrosion inhibitor on the electrochemical behavior of 316L and 304L concrete reinforcement in a simulating concrete pore solution exposed to aggressive environments, i.e. acid rain, is the main objective of the present study. The corrosion performance of 316L and 304L stainless steel is examined by means of cyclic (reverse) polarization in order to evaluate the susceptibility of the rebars to localized corrosion. Two types of electrolyte were used. The first electrolyte is a highly alkaline solution simulating fresh concrete exposed to acid rain (pH » 12), while the second electrolyte is a mildly alkaline solution simulating corroded concrete cover that exposed the reinforcement to direct acid rain attack (pH » 8). Both solutions contained saturated Ca(OH)₂, an acid rain simulating solution and FA (0 wt.% - 25 wt.% of the dry mixture) as corrosion inhibitor. In both electrolytes the beneficial effect of FA up to 20 wt.% content on the corrosion resistance of both 316L and 304L rebars was manifested. However, this trend was reversed at 25 wt.% content due to the localized presence of agglomerates of FA on the surface of the steel. The above finding was confirmed by SEM/EDX examination of cross-sections after cyclic polarization. An important conclusion of this study was the feasibility of replacing 316L stainless steel with 304L in critical applications, such as the restoration of ancient monuments, provided that FA is included in the concrete mixture, even at low contents (10 or 15 wt.%).

Phytochemicals are chemical compounds produced by plants that play key roles in their growth and defense and have also been actively involved in corrosion inhibition of metals and alloys. The action of these phytochemicals as inhibitor molecules in an aggressive environment is triggered by the presence of heteroatoms and other adsorption sites capable of chelating with the metal ions forming complexes that provide a protective film for the metal. This protective film blocks the active sites on the metal from further interaction with the aggressive environment. The efficiency of corrosion inhibitors in coating formulations requires the compounds to be safely encapsulated prior to when triggered. This prevents leaching and early interactions with the coating matrix and is a preferred carrier mode than when directly spiked in the coating matrix. The flavonoid Quercetin (QCT) present in a wide variety of plants was explored. QCT contains five electroactive hydroxyl groups in addition to the carboxylic, carbonyl, and aromatic groups which provides three potential coordination sites for interaction with the metal ions. When loaded in silica nanocontainers, the phytochemical was evaluated for active corrosion protection of aluminium alloy 6061 in the prepared self-healing coatings. The corrosion protection offered by QCT was investigated with electrochemical impedance spectroscopy in an aggressive chloride environment. Chemical transformation experienced by QCT was influenced by pH and a protective film was detected in the defective zone of the examined coupons.

Abstract: Metal additive manufacturing is proving to be a rapidly emerging technology that promises to make considerable disruption to manufacturing practices worldwide. The ability to 3D print metals allows for fast-prototyping, complex designs and direct at-location manufacturing of parts using minimal materials, waste and cost. Wire arc additive manufacturing (WAM) is the leading contender for commercial large-scale 3D metal part production due to its high deposition rate. However, corrosion and degradation behaviour of 3D printed metals are yet to be well-explored and is expected to be different from conventional manufacturing, due to the anisotropy imposed by the layer-by-layer additive process of fabrication. In collaboration with AML3D: a world-leader in large-scale 3D metal WAM, stainless steel and aluminium alloys were investigated due to their desirable weight-to-strength and corrosion resistant qualities. A review of current literature on WAM printing parameters and their influence on microstructure, corrosion behaviour and part degradation reveals little in the area. We report our efforts on 316 stainless steel and aluminium bronze alloys that have been WAM printed, varying the deposition rate, material heating and wire feed velocity. Studies of the corrosion behaviour and microstructure have been investigated using accelerated potentiodynamic corrosion testing and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution, followed by surface characterisation by scanning electron and auger electron spectromicroscopy (SEM and AES/SAM).

Hot Cr target magnetron sputtering with radio-frequency inductively-coupled plasma (RF-ICP) source and separate gas (Ar+N₂) inlets were used to obtain CrN_x coatings. Higher deposition rates (137 nm/min) can be obtained using hot Cr target due to its sublimation at elevated temperatures in comparison with conventional reactive magnetron sputtering (10-50 nm/min). While the separated gas (Ar, N₂) inlets and RF-ICP assistance were applied to improve stability and decrease hysteresis effects of deposition process. The corrosion behavior of the CrN_x coatings was investigated by potentiodynamic method in a 3.5wt% NaCl solution in the range from -800 to 800 mV with a sweep rate of 0.5 mV/s. Results of the tests have shown the role of deposition parameters on corrosion resistance of the coatings. Pure chromium and CrN coatings had the lowest corrosion rate in 3.5wt% NaCl solution, when the substrate bias potential was equal to -100 V. Under these deposition conditions, the coatings had higher hardness (11.2 and 21.3 GPa for Cr and CrN) and denser columnar microstructure in comparison with the coatings obtained at lower bias potential. The reported study was funded by RFBR according to the research project № 20-38-90134.

Plasma-facing materials (PFMs) must be able to withstand conditions that are more extreme than anything naturally met on the face of the earth. Under the high particle and heat fluxes experienced in fusion plasma situations, cracking, surface roughening, blistering, hole formation, and melting have all been observed on tungsten PFMs. Degradation to PFMs in this way can lead to decreased performance in fusion reactors. Continued research and development of materials with properties that improve performance and minimise material degradation of the PFM is critical. This study compares diamond-like carbon (DLC) coatings and tungsten-doped DLC (W-DLC) coatings on pure polycrystalline tungsten substrates that have been exposed to hydrogen plasma. DLC coatings were prepared by plasma-assisted chemical vapour deposition (PECVD) with methane gas as the carbon source, in an RF plasma chamber. W-DLC coatings were prepared layer-by-layer via argon ion sputtering for the deposition of a tungsten layer between DLC layers. We present the results of coating of varying thickness that were prepared by altering the RF power, gas pressure and deposition time. The samples were exposed to a hydrogen plasma for a total of 120 hours. Changes in coating elemental composition and topography after exposure were observed by Auger and scanning electron spectromicroscopies. The thickness of each coating can be optimised to minimise degradation to tungsten PFMs, thereby improving the performance of fusion reactors.

Biobased polymers and composites have gained increased global attention due to their abundant availability, renewability and biodegradability. Natural fillers, e.g. cellulose-based fillers, improve mechanical properties of biopolymers extending their application range, while keeping the ecofriendliness of the materials. Mowing towards engineering applications, requirements imposed to materials’ durability under environmental impact are increasing. Variations of ambient humidity and temperature could essentially reduce service lifetime of biobased polymer composites. This study is focused on hydrothermal degradation of poly(butylene succinate) (PBS) filled with nanofibrillated cellulose (NFC) up to 50 wt.% aimed to identify the most efficient PBS/NFC composition, while keeping a reasonable balance between the reinforcement effect and accelerated degradation inherent for most natural fillers. Water absorption and its effect on the structure, thermal, mechanical and thermomechanical properties were studied. Reasonably high reinforcement and adhesion efficiency is obtained for PBS/NFC composites that is maintained after their hydrothermal ageing. Water absorption capacity and diffusivity increased significantly with NFC content in PBS. Degradation of the mechanical properties is the higher, the higher NFC content in the polymer is. PBS filled with 20 wt.% of NFC is identified as the most efficient composition, for which negative environmental degradation effects are counterbalanced with the positive reinforcing effect.

Crucial accidents at the Three Mile Island and Fukushima nuclear power plants occurred as a result of loss of coolant (LOCA) and bursts of reactivity. It showed a danger of a rapid reaction of steam with zirconium at high temperatures. Nowadays, a lot of science groups are developing accident tolerant nuclear fuel (ATF).
This work is devoted to study of oxidation resistance of zirconium E110 alloy with a protective coating of chromium. For this, several series of E110 samples were prepared using by using magnetron sputtering and investigations of their resistance under normal operation and LOCA scenarios were performed.
It was shown the role of deposition technology on the coating properties (thickness, microstructure, mechanical parameters, adhesion), resistance to oxidation during autoclave tests (360 ° С, 186 atm) and LOCA conditions.
The studies showed that surface modification of zirconium fuel cladding by chromium coating can significantly reduce its oxidation, increase the time until zirconium start to interact with oxygen and improve the safety of light water nuclear power reactors.
The work was supported by the Russian Science Foundation [grant No. 19-79-10116].

Organic compounds, added in a small amount to corrosive solution, have been used for decades as inhibitors of metal corrosion. Usually, the organic compound is chemisorbed on the metal surface thus forming a protective layer which is able to retard the metal dissolution. This system is quite complex and the final result, i.e. the level of protectiveness, depends on the properties of organic molecule, properties of the substrate and of the corrosive medium. Experimental efforts in the past decades have accumulated large amounts of research evidence for the protectiveness of various systems but there is still no simple method to predict how an organic molecule would perform on a selected metal. This work therefore addresses the basic relationships between aluminum surfaces and corrosion inhibitors. To achieve that, we first designed a series of organic compounds which differed in the (a) type of backbone chain (alkyl and perfluoro), (b) length of backbone chain, and (c) type of anchor group. Thereafter, the experiments were utilized in such a way to allow the investigation of the effect of the inhibitor's anchor group and the backbone chain on their performance against corrosion of aluminum in chloride solution.

The present study invokes on the assessment of the anticorrosive efficiency of zinc phosphate (ZP) and epoxy resin (DGEBA-DAA) based composite (DGEBA-DAA-ZP) for electrolytic cadmium pre-treated 15CDV6 steel in 3wt% NaCl medium. The composite formulation (DGEBA-DAA-ZP) performances as effective anti-corrosive coating at different exposure times ranging from 60, 120 and 180 days in a salt spray chamber. Electrochemical impedance spectroscopy (EIS) and molecular dynamic (MD) simulations were used to illustrate the anti-corrosive property of the composite. EIS study revealed that the composite acted as strong interface inhibitor and the anticorrosive behavior decreases with increasing the exposure time. Similarly, results reveal that the longer the exposure time, the lower the magnitude of charge transfer resistance (R_ct) and coating resistance (R_pore). Results of MD simulation showed that the flat or nearly flat orientation of the DGEBA-DAA-ZP adsorbed on the Cd surface behaved as efficient anti-corrosive material.

Titanium Grade 4 (G4) is the most commonly used material for dental implants due to its excellent biocompatibility and mechanical properties. However, titanium implants require a rough surface that can increase the biomechanical potential of implant-bone contact and affect protein adsorption speed. In this work, the effect of sandblasting of Ti G4 surface on the long-term corrosion resistance in artificial saliva of pH = 7.4 at 37 °C was studied. The X-ray diffraction (XRD) single-{hkl} sin²ψ method was used to measure the sandblasted Ti residual stress. In vitro corrosion resistance tests were conducted for 21 days using the open circuit potential method, polarization curves, and electrochemical impedance spectroscopy. Using the Kelvin scanning probe, the electron work function was determined. Analysis of the obtained results showed an improvement in the corrosion resistance of the sandblasted Ti G4 compared to Ti with the machine surface. The increase in corrosion resistance was related to the residual compressive stresses of 324(7) MPa present in the sandblasted Ti surface. Sandblasting caused plastic deformation of the Ti surface, which resulted in the improvement in mechanical properties, as evidenced by the increase in the hardness of the sandblasted Ti compared to Ti with the machine surface.