Facile fabrication of novel superhydrophobic Al2O3/polysiloxane hybrids coatings for aluminum alloy corrosion protection

Heat Resistant Poly(carborane-siloxane) Adhesives

Organic adhesives have been extensively utilized in electronic manufacturing, automotive assembly, and household applications owing to their ease of processing, lightweight nature, and robust adhesion. However, organic chain oxidation and degradation under high temperatures induced catastrophic material failure in harsh environments like aerospace systems. To overcome this limitation, a series of vinyl-functionalized poly(carborane-siloxane) (PCS-x%) is synthesized via a one-pot method, subsequently crosslinked with 0.9 wt.% 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane to fabricate high-temperature adhesives (c-PCS-x%). The crosslinking density of the c-PCS-x% is modulated by adjusting the vinyl side group content in the PCS-x%. All c-PCS-x% demonstrated good thermal stability with less than 10% weight loss during degradation, particularly c-PCS-75% achieving the lowest weight loss of 3.6%. Thermal stabilization mechanisms are attributed to the crosslinked networks' suppressed borane fragment volatilization through covalent bonding and enhance cohesive energy by increased cross-linking density. The crosslinked c-PCS-x% adhesives surpass the linear analog (c-PCS-0%) in adhesion strength across temperatures ranging from room temperature to 250 °C. Notably, c-PCS-25% maintain 5.68 MPa adhesion strength post-aging at 200 °C/24 h and endure an ablation test for 10 min while sustaining a 1 kg load. This work establishes a novel molecular design for harsh environment adhesives through topology-controlled poly(carborane-siloxane) networks.

Investigation of sol-gel derived organic inorganic hybrid coatings based on commercial epoxy resin for improved corrosion resistance of 304 stainless steel

In this study, a commercial epoxy resin (KER 828) was employed as the organic component of the organic inorganic hybrid coating to enhance corrosion resistance while reducing production costs via the sol-gel method. Hybrid coatings were formulated with varying weight percentages and subsequently applied to 304 stainless steel substrates to assess their effectiveness against corrosion. The Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), pull off test and water contact angle (WCA) techniques were employed to characterize the obtained coatings. The corrosion behavior of both the uncoated stainless steel and the coated samples was evaluated through Potentiodynamic Polarization test. Additionally, the electrochemical impedance spectroscopy (EIS) analysis was employed over time intervals of 1 h, 1 day, 1 week and 1 month exposure to 3.5 wt% NaCl solution. The results demonstrated that coatings with equal weight percentages of the organic and inorganic phases (1:1:1) exhibited the highest corrosion resistance, which can be attributed to the enhanced Si-O-Si network formation. Then SiO2 nanoparticles were incorporated into the optimal coating formulation to examine the barrier effect and the impact of nanoparticles presence on the hybrid coating performance (1:1:1:0.01). The results acquired from Potentiodynamic polarization (Ecorr of - 0.327 V and icorr of 9.83 × 10-11 A.cm-2), EIS (Rct of 158320 Ω.cm2 after 1 month of immersion) and WCA (81.67°) analysis indicated that coating containing SiO2 nanoparticles (1:1:1:0.01) provided superior surface protection compared to all other synthesized hybrid coatings.

Fabrication of biochar-based superhydrophobic coating on steel substrate and its UV resistance, anti-scaling, and corrosion resistance performance

In this study, we report an eco-friendly and facile process for the synthesis of biochar, BC, and a cobalt-biochar nanocomposite, Co-BC, using rice straw biomass. We constructed two superhydrophobic coatings on steel substrates using potentiostatic electrodeposition of nickel-modified biochar, Ni@BC, and nickel modified by cobalt-biochar nanocomposite, Ni@Co-BC, then, these coatings were soaked in an ethanolic stearic acid solution. Fourier transform infrared spectroscopy showed that the stearic acid-grafted Ni@BC coating, Ni@BC@SA, and the stearic acid-grafted Ni@Co-BC composite, Ni@Co-BC@SA, were well grafted on the steel surface. Scanning electron microscopy revealed that the superhydrophobic coatings have nanoscale features. Atomic force microscopy results showed that the Ni@Co-BC@SA coat had higher roughness than Ni@BC@SA, resulting in higher superhydrophobicity. The water contact angles for Ni@BC@SA and Ni@Co-BC@SA coatings were 161° and 165°, respectively, while the values of water sliding angles for both coatings were 3.0° and 1.0°, respectively. Quantitative estimation of the scale inhibition efficiency revealed that the Ni@Co-BC@SA coating exhibited greater efficiency compared to the Ni@BC@SA coating. Additionally, the Ni@Co-BC@SA coating demonstrated improved corrosion resistance, UV resistance, mechanical abrasion resistance, and chemical stability compared to the Ni@BC@SA coating. These results highlight the superior performance of the Ni@Co-BC@SA coating and its potential as a highly effective and durable superhydrophobic coating for steel substrates.

Icing behavior of supercooled droplets on superhydrophobic polymercoatings between lotus effect and petal effect

This paper investigated anti-icing behavior and wettability of droplets on superhydrophobic polymercoatings between lotus effect and petal effect, which were prepared on surfaces of 2021 aluminum alloy with 1H, 1H, 2H, 2H-heptafluorodecyl (FAS-17). The prepared surfaces displayed excellent hydrophobicity with contact angles of 154.9° ± 1.5°and 139.8° ± 1.3°, while rolling angles are 4° ± 1.0° (lotus effect) and 30° ± 1.5° (petal effect). Thus, the present study focused on the different characterizations and the anti-icing potential of the superhydrophobic polymersurfaces were analyzed based on three parameters including the icing delay time, the crystallization temperature of water droplets, and contact time of impinging droplets on the cold superhydrophobic polymer coatings (−15 °C). Furthermore, the anti-icing of superhydrophobic coatings between lotus effect and petal effect with freezing time and crystallization temperature experimental phenomena were consistent with the thermodynamic analysis. It is also proved that the droplets have different bounce behavior on different polymercoating surfaces by droplet impact experiment. The study offers a comprehensive perspective on polymercoatings of different wetttablility for anti-icing behavior applications.

Green Corrosion Inhibition on Carbon-Fibre-Reinforced Aluminium Laminate in NaCl Using Aerva Lanata Flower Extract

Aluminium-based fibre–metal laminates are lucrative candidates for aerospace manufacturers since they are lightweight and high-strength materials. The flower extract of aerva lanata was studied in order to prevent the effect of corrosion on the aluminium-based fibre–metal laminates (FMLs) in basic media. It is considered an eco-friendly corrosion inhibitor using natural sources. Its flower species belong to the Amaranthaceae family. The results of the Fourier-transform infrared spectroscopy (FTIR) show that this flower extract includes organic compounds such as aromatic links, heteroatoms, and oxygen, which can be used as an organic corrosion inhibitor in an acidic environment. The effectiveness of the aerva-lanata flower behaviour in acting as an inhibitor of the corrosion process of FMLs was studied in 3.5% NaCl solution. The inhibition efficiency was calculated within a range of concentration of the inhibitor at room temperature, using the weight-loss method, potentiodynamic polarization measurements and electrochemical-impedance spectroscopy (EIS). The results indicate a characterization of about 87.02% in the presence of 600 ppm of inhibitor. The Tafel curve in the polarization experiments shows an inhibition efficiency of 88%. The inhibition mechanism was the absorption on the FML surface, and its absorption was observed with the aid of the Langmuir adsorption isotherm. This complex protective film occupies a larger surface area on the surface of the FML. Hence, by restricting the surface of the metallic layer from the corrosive medium, the charge and ion switch at the FML surface is reduced, thereby increasing the corrosion resistance.