Innovative coatings for corrosion protection of historical aluminium alloys in aerospace heritage

Using acrylamide and oligo (oxyethylene) methacrylate in corrosion protection of steel

Cardiovascular diseases cause the highest global mortality rates and are often treated with surgical interventions such as stent or vascular plug placement. However, in-stent restenosis develops over time depending on the material composition and interactions with body fluids. Current strategies to address restenosis include balloon angioplasty or placing a secondary stent at the same site. A key concern with overlapping stents is the increasing risk of galvanic corrosion, as most cardiovascular stents have metallic composition. This study examines galvanic corrosion rates in different vascular stent and plug combinations using electrochemical corrosion characterization techniques. Three metallic vascular specimens with varying compositions are evaluated. The specimens are immersed in simulated body fluid at 37°C under individual and overlapping conditions. Electrochemical impedance spectroscopy and current density measurements, conducted via potentiostat, provide insights into the corrosion behavior of each specimen configuration. Additionally, inductively coupled plasma mass spectrometry quantifies metal ion release through SBF samples. Results show that combining dissimilar materials in overlapping placements significantly increases galvanic corrosion and metal ion release. The corrosion current density (icorr) significantly increased from 11.75 μA/cm2 in the individual bare-metallic stent to 522.3 μA/cm2 in the stent-on-plug configuration. A similar increase was observed in the stent-on-stent configuration, with an icorr of 132.6 μA/cm2. These results corresponded with notable decreases in electrochemical impedance and polarization resistance, measured as low as 0.039 kΩ (ZT) and 0.057 kΩ cm2 (RP) for the stent-on-plug system. Consequently, the calculated corrosion rate escalated to 2254 μm/year, with a mass loss reaching 42.22 mg/cm2·year. ICP-MS analysis supported these findings, showing the highest levels of metal ion release in the stent-on-plug configuration, with 23.86 ppm of Ni and 0.41 ppm of Cr. These findings highlight the importance of stent-material selection in reducing corrosion-related complications. Implementing material-specific strategies in secondary stent placement can lower the risks of inflammatory host response, stent failure, and their long-term effects.

Long term stability of biodegradable polymers on building limestone

Fabrication of dual self-healing silane nanocomposite for efficient corrosion protection of aluminum alloy

The use of a hydraulic binder for the treatment of mineral‐based industrial wastes, containing heavy metals, by the chemical fixation and solidification (CFS) technique has raised serious questions regarding the prediction of the behaviour of these pollutants in the obtained solid matrix. It seems necessary, for this reason, to study the behaviour of these metals in response to leaching in order to evaluate their chemical speciation within the solidified sludge over the medium and long‐terms. Within the framework of the current research, we applied the CFS technique to metallic hydroxide sludge, produced by the electrotyping surface treatment industry, by using Portland artificial cement (PAC). Compaction at the paste phase of this treated sludge resulted in up to 35% enhancement of the retention of pollutants, mainly trivalent chromium, in a cementing matrix, as compared with the classical technique that uses a simple vibration of sludge at the paste phase. The implemented process led to an improvement in the compactness of the sludge, and thus assured a better retention of heavy metals in response to the leaching of this treated sludge. The evaluation of the chemical properties of the materials obtained after an artificial ageing process using humidity variation cycles and thermal chocks also revealed a significant improvement in the retention capacity of heavy metals in the solidified sludge, which was mainly favoured by the development of carbonation. In fact, the release of the heavy metals from the above mentioned treated sludge was reduced by 58% for zinc and 51% for trivalent chromium after the artificial ageing process.

Natural organic antioxidants from green tea inhibit corrosion of steel reinforcing bars embedded in mortar

Solid oxide fuel cells (SOFCs) operating at intermediate temperature (500 – 700 °C) have attracted much attention due to high energy conversion efficiency, fuel adaptability and low emissions [1]. Both composition and microstructural /architectural design of the cathode film play an important role in obtaining the optimal electrochemical performances in this temperature range [2-9]. Recently, Ln2NiO4+δ (Ln = La, Pr, Nd) rare-earth nickelates have displayed promising oxygen electrode performance because of their interesting structure, transport and catalytic performance. Among nickelates, Pr2NiO4+δ presents excellent electrochemical properties at intermediate temperatures while it is characterized by a rather poor chemical stability in comparison to La2NiO4+δ. The preparation of efficient oxygen electrode materials which present very low degradation rates is still a challenge. The present study is focused on designing Pr doped lanthanum nickelates, La2-xPrxNiO4+δ with 0 ≤ x ≤ 2 with the aim of finding the best compromise between chemical stability and optimized electrochemical performance. First, single and double layered La2NiO4+δ electrodes with controlled microstructure were deposited on Ce0.9Gd0.1O2-δ (CGO) electrolyte using electrostatic spray deposition (ESD) or/and screen-printing (SP). The microstructure of La2NiO4+δ films has been optimized by varying some key process parameters. A coral-like microstructure of La2NiO4+δ films was successfully obtained resulting from nozzle to substrate distance, flow rate, substrate temperature deposition time equal to 50 mm, 1.5 mL/h, 350 °C and 3 h, respectively [6]. Electrochemical properties of La2NiO4+δ deposited symmetrically on CGO were measured by impedance spectroscopy. They are found to be strongly dependent on the cathode microstructure and architecture. For example, a double layer La2NiO4+δ cathode, consisted of 3-D coral nanocrystalline film (average particle size ~ 150 nm) with a continuous nanometric dense sub-layer (100 nm) at the electrode/electrolyte interface, prepared by ESD and topped by a La2NiO4+δ current collector prepared by SP, shows the best performance leading to the polarization resistance (Rpol) down to 0.42 Ω cm² at 600 °C (Fig 1) [6]. In a second part, this double layer design was extended toLa2-xPrxNiO4+δ (with x = 0, 0.5, 1 and 2) cathodes with a view to taking advantage of the complimentary properties of the two extreme compositions Pr2NiO4+δ and La2NiO4+δ, i.e. higher electronic conductivity of Pr2NiO4+δ superior stability of La2NiO4+δ. The chemical stability and polarization resistance (Rpol) were found to decrease when the Pr content was increased. Polarization resistance (Rpol) equal to 0.42, 0.12 and 0.08 Ω cm2 at 600 °C has been obtained for La2NiO4+δ, LaPrNiO4+δ and Pr2NiO4+δ, respectively. Among the complete La2-xPrxNiO4+δ solid solution, LaPrNiO4+δ shows the best compromise between electrochemical properties (the lowest Rpol value available in the literature for this composition, 0.12 W cm2 at 600 °C) and chemical stability in air (up to 30 days at 700 °C) [9]. Finally, the role of the electrode/electrolyte interface has been investigated on the polarization resistance of La2NiO4+δ and Pr2NiO4+δ cathodes. For this purpose, the thin dense nickelate sub-layer was replaced by a thin porous (~3-4 mm) composite layer based on a mixture of CGO (deposited by SP) and La2NiO4+δ or Pr2NiO4+δ (deposited by ESD). As a consequence, further reduction in Rpol down to 0.16 (Fig 1) and 0.04 Ω cm2 was successfully obtained for La2NiO4+δ and Pr2NiO4+δ, respectively [8]. This composite LnNO-CGO sub-layer is playing an important role in enhancing the electrochemical properties of these cathodes leading to the lowest Rpol values available in the literature for these compositions, to the best of our knowledge. This talk will end with our latest results incorporating a LnNO-CGO composite sub-layer to the double layer LaPrNiO4+δ electrode, the most promising composition in terms of electrochemical properties and chemical stability.

Research on protection of the architectural glazed ceramics in the Palace Museum, Beijing

Enhancement of active thin-layer capping with natural zeolite to simultaneously inhibit nutrient and heavy metal release from sediments

Currently used organic coatings for the protection of bronze sculptures have a relatively short lifespan as a consequence of strict requirements of conservation ethics, which limit the selection of coatings. For that reason, enhancement of the corrosion protection level and durability of appropriate coatings is needed. The aim of this work was to examine if corrosion protection of bronze by selected acrylic and polyurethane coatings could be improved by using two phosphonic acids, 16-phosphonohexadecanoic acid (COOH-PA) and 12-aminododecylphosphonic acid (NH2-PA). Electrochemical measurements (linear polarization and electrochemical impedance spectroscopy, EIS) were performed to gain an insight into the influence of these phosphonic acids on the performance of the coatings during a two-week exposure to artificial acid rain and a three-month outdoor exposure. Besides the influence on the corrosion protection level, the influence on the coating adhesion was examined as well. A pull-off test clearly confirmed that the studied phosphonic acids act as adhesion promoters of both polyurethane and acrylic coatings, while electrochemical studies revealed improvements in corrosion protection levels, especially in the case of the acrylic coating Paraloid B72.

The role of indigenous microorganisms in the biotransformation of refractory organic-rich copper-bearing black shale ore (Kupferschiefer) was confirmed in laboratory experiments. The persistent shale's organic matter was utilized by a mixture of bacterial strains as the sole carbon and energy source, and bacterial growth was accompanied by chemical and structural changes of black shale. The release of metallic elements and organic compounds into the aqueous phase was shown. Chemical analysis revealed the presence of long-chain aliphatic hydrocarbons and further biodegradation of these compounds by bacterial action. In this study, the release of metals from metalloorganic compounds present in organic-rich copper-bearing black shale was shown for the first time. The results have also confirmed the biotransformation of metalloporphyrins naturally occurring in black shale by indigenous microorganisms. Moreover, changes in the surface area and quantitative mineral composition of black shale were detected following bacterial treatment. This biotransformation activity is of potential use in biotechnological procedures for the recovery of copper and other valuable metals from tailings that contain up to 16% black shale. On the other hand, the release of organic carbon and heavy metals from black shale by biodegradation may significantly add to anthropogenic pollution.

Polyurethane (PU) coatings have a wide demand in industry and are used for the protection of metal, concrete and wood structures. However, PU coatings face challenges in regard to circular economy concepts. Although waterborne solvent formulation techniques as well as naturally derived monomers are compatible with a circular economy, PU coatings possess a strong barrier. In this study, a series of PU coatings were prepared using water as the main solvent, and the polyol and chain extender monomers used were prepared from natural resources. The synthesized PU coating showed UV resistance, fire retardancy and corrosion protection. The exposed PU coating was collected and used with Portland cement.

Thermal characterization of new, artificially aged and historical leather and parchment

This work evaluates the effectiveness of coating bronze coupons, with 3% Benzotriazole (BTA) -loaded nanocontainers mixed with Paraloid polymer. Mesoporous silica nanoparticles (MSNs) were prepared and loaded with 3% BTA (BTA@MSNs) followed by dispersion in 3% Paraloid B72 and B44. Bronze disc samples with the chemical composition of Cu 85%, Sn 10% and Pb 5% simulating archaeological artifacts were coated with a single and double layer of BTA@MSNs in Paraloid B72 and B44 and evaluated using several techniques. Colorimetric measurements (CM) were used to evaluate changes in the surface appearance following the coating with single and double protective layers. The corrosion inhibitive performance of the coating was investigated using electrochemical impedance spectroscopy (EIS). Transmission electron microscope (TEM) was performed to characterize the shape and size of the prepared SiO2 nanoparticles, while X-ray Diffraction (XRD) was performed to confirm the presence of amorphous mesoporous SiO2 nanoparticles. The specific surface area, pore volume and pore size distribution were measured by nitrogen adsorption– desorption technique, while the release rate of benzotriazole at various experimental pH values was estimated using UV–Vis spectroscopy. Results confirmed the sustained release of benzotriazole to varying pH levels. The release was higher with an increase in the pH of the medium, which signifies that the release rate rises in the alkaline medium. The best corrosion inhibitive performance was for the double layer BTA@MSNs – B72 samples at 91.73% efficiency, while single layer BTA@MSNs – B72 samples displayed the least change in color ΔE 3.28.

This study introduces a robust, self-healing superhydrophobic coating for magnesium (Mg) substrates, leveraging the synergistic effects of MQ organosilicon polymer, octadecylamine (ODA), polydopamine (PDA), and copper-loaded graphene oxide (GO). The coating exhibits exceptional superhydrophobicity, outstanding stability in harsh environments, superior resistance to smudging, and effective self-cleaning capabilities. Electrochemical impedance spectroscopy (EIS) in 3.5 wt % NaCl solution demonstrates an impedance modulus (|Z|) at f = 0.01 Hz and polarization resistance (Rp) of 3.49 × 108 Ω cm2 and 3.88 × 108 Ω cm2, respectively, 7 orders of magnitude higher than AZ31B. After 35 days of immersion, |Z|f=0.01Hz and Rp remain at 3.97 × 107 Ω cm2 and 4.63 × 107 Ω cm2, respectively, highlighting long-term corrosion protection. In cases of damage or corrosion, the dynamic coordination of PDA-Cu2+ enables self-healing, fully recovering visible coating defect up to 10 μm in width within 24 h in 3.5 wt % NaCl solution. This work presents a promising approach for durable, self-healing superhydrophobic coatings with exceptional mechanical and chemical stability.