Water-soluble chitosan salt as ecofriendly corrosion inhibitor for N80 pipeline steel in artificial sea water: Experimental and theoretical approach.

Chitosan, as a proficient biopolymer, has enormous potential as an ecofriendly corrosion inhibitor (CI), but their limited solubility restricts practical applications. Herein, an eco-friendly and water-soluble chitosan salt (CS) was utilized as a green CI on N80 pipeline steel in artificial sea water. Several structural and surface analytical tools were engaged in describing the characteristics of novel CS polymer. The corrosion inhibition efficiencies of CS on steel at different concentrations were investigated through gravimetric, conventional and advanced electrochemical techniques along with the surface analyses. Tafel polarization tests specified that CS performed as mixed-type CI with prevalent anodic inhibition characteristics. At a concentration of 1000 ppm, CS provided an inhibition efficiency (IE) of 96.68 %, following physiochemical adsorptions of CS on N80 surface validated by fitting Langmuir adsorption isotherm. However, the reductions in the values of IE at high temperature specified that the CS is the temperature dependent CIs. Scanning electrochemical microscopic evaluation confirmed the formation of thin CS inhibitors films with high electrochemical stability on N80 steel in saline. The performed surface characterizations on inhibited surfaces validated the adsorption of CS on the N80 surface by forming thin inhibitor film to obstruct metal corrosion. The theoretical simulation studies using molecular dynamics and density functional theory corroborated the experimentally obtained results.

Ti-30Nb-3Ag alloy with improved corrosion resistance and antibacterial properties for orthopedic and dental applications produced by mechanical alloying.

Titanium alloys have gained popularity as a bioimplant material due to their biocompatibility, low modulus of elasticity, and increased strength. However, other issues, such as corrosion resistance, and infections can reduce the implant's lifespan. This paper aims to fabricate a new Ti-30Nb-3Ag at% alloy with enhanced in vitro corrosion and antibacterial properties by mechanical alloying (MA) followed by powder consolidation. XRD, SEM/EDX, and Vickers microhardness analyses were used to examine the phases compositions, microstructure, and microhardness, respectively. The in vitro corrosion performance of Ti-30Nb-3Ag alloy was inspected in a simulated body medium and artificial saliva. The alloy's antibacterial properties were evaluated in the gram-positive and negative bacterial medium. The results showed that after MA for 60 h, nanocrystalline ß-Ti (BCC) and α-Ti (HCP) solid solutions were formed with crystallite sizes of 7.44 and 3.47 nm, respectively. The sintered sample exhibited densifications of 97%, with a microstructure composed of ß-Ti, α-Ti, and a minor quantity of ultrafine Ti2Ag phase. The microhardness result showed that Ti-30Nb-3Ag alloy possesses HV 491.5. Ti-30Nb-3Ag alloy has a potent antibacterial capability of 85.75% and 88.81% relative to Ti-6Al-4V alloy and CP-Ti, respectively. In vitro corrosion results revealed that the Ti-30Nb-3Ag alloy exhibited the widespread passive area in the investigated anodic regions and presented the highest impedance values in comparison with the commercial alloys, confirming its improved corrosion resistance performance in both studied mediums. Ti-30Nb-3Ag alloy possibly be a competitive bioimplant material for orthopedic and dental uses owing to its enhanced biocorrosion and antibacterial properties compared to commercial Ti-6Al-4V alloy and CP-Ti.

UV-Protected Polyurethane/f-Oil Fly Ash-CeO2 Coating: Effect of Pre-Mixing f-Oil Fly Ash-CeO2 with Monomers.

A series of UV-protected coatings were prepared using cerium-oxide-functionalized oil fly ash (f-OFA-CeO2) in waterborne polyurethane (WBPU) dispersions. Three monomers, namely, poly(tetramethyleneoxide glycol) (PTMG), polydimethylsiloxane-hydroxy terminated (PDMS) and 4,4-dicyclohexylmethane diisocyanate (H12MDI), were used to pre-mix with f-OFA-CeO2 separately, followed by the synthesis of WBPU/f-OFA-CeO2 dispersions. The f-OFA-CeO2 distribution and enrichment into any part (top/bottom/bulk) of the coating was strongly affected by the pre-mixing of f-OFA-CeO2. The f-OFA-CeO2 was densely distributed in the top, bottom and bulk when the f-OFA-CeO2 was pre-mixed with PDMS, H12MDI and PTMG, respectively. Only an f-OFA-CeO2-enriched top surface showed excellent UV protection. The lowest UV-degraded exposed coating was found when the top surface of the coating was f-OFA-CeO2-enriched.

Multi Self-Healable UV Shielding Polyurethane/CeO2 Protective Coating: The Effect of Low-Molecular-Weight Polyols.

We prepared a series of polyurethane (PU) coatings with defined contents using poly(tetramethylene oxide)glycol (PTMG) with two different molecular weights (i.e., Mn = 2000 and 650), as well as polydimethyl siloxane (PDMS) with a molecular weight of Mn 550. For every coating, maximum adhesive strength and excellent self-healing character (three times) were found using 6.775 mol% mixed with low-molecular-weight-based polyols (PU-11-3-3). Defined 1.0 wt% CeO2 was also used for the PU-11-3-3 coating (i.e., PU-11-3-3-CeO2) to obtain UV shielding properties. Both the in situ polymerization and blending processes were separately applied during the preparation of the PU-11-3-3-CeO2 coating dispersion. The in situ polymerization-based coating (i.e., PU-11-3-3-CeO2-P) showed similar self-healing properties. The PU-11-3-3-CeO2-P coating also showed excellent UV shielding in real outdoor exposure conditions.

Preparation and characterization of Pectin/Polypyrrole based multifunctional coatings on TiNbZr alloy for orthopaedic applications.

Being a natural and renewable polysaccharide, pectin (PC) is considered a polymer with promising potential for many applications. In the present investigation, novel multifunctional pectin/polypyrrole (PC/PPy) composite coatings loaded with gentamicin (GM) were electrochemically deposited on TiNbZr alloy to enhance its biocompatibility, antibacterial performance and corrosion resistance in physiological environment. Various surface and structural characterization techniques were deployed to examine the composite coatings. in vitro corrosion analysis confirmed that the composite coated TiNbZr specimen exhibited higher corrosion resistant performance in simulated body fluid (SBF). The drug release kinetics was estimated and the results corroborated the sustained release of GM from the controlled degradation of the composite matrix. The pectin composite coatings exhibited effective antibacterial performance; due to the sustained release of GM. In-vitro cell culture studies validated the improved biocompatibility of the composite coatings. Among the developed coatings, composite coatings loaded with 10 wt. % of GM exhibited the lowest corrosion rate, enhanced biocompatibility, and antibacterial performance.

Tribological and Electrochemical Characterization of UHMWPE Hybrid Nanocomposite Coating for Biomedical Applications.

A new approach of using a polymer hybrid nanocomposite coating to modify the surface of titanium and its alloys is explored in this study. Electrostatic spray coating process is used to deposit the coating on the plasma-treated substrates for better adhesion. Ultra-high molecular weight polyethylene (UHMWPE) has been selected as the parent matrix for the coating due to its biocompatibility and excellent tribological properties. However, to improve its load-bearing capacity carbon nanotubes (CNT's) (0.5, 1.5, and 3 wt.%) are used as reinforcement and to further enhance its performance, different weight percent of hydroxyapatite (HA) (0.5, 1.5, 3, and 5 wt.%) are introduced to form a hybrid nanocomposite coating. The dispersion of CNT's and HA was evaluated by Raman spectroscopy and scanning electron microscopy. The electrochemical corrosion behavior of the nanocomposite coatings was evaluated by performing potentiodynamic polarization and electrochemical impedance spectroscopic tests in simulated body fluid. Tribological performance of the developed hybrid nanocomposite coating was evaluated using a 6.3 mm diameter stainless steel (440C) ball as the counterface in a ball-on-disk configuration. Tests were carried out at different normal loads (7 N, 9 N, 12 N, and 15 N) and a constant sliding velocity of 0.1 m/s. The developed hybrid nanocomposite coating showed excellent mechanical properties in terms of high hardness, improved scratch resistance, and excellent wear and corrosion resistance compared to the pristine UHMWPE coatings.

Water-Erodible Xanthan-Acrylate-Polyurethane Antifouling Coating.

Biopolymer xanthan (Xn) and its functionalized polymer xanthan acrylate (XnAc) were used to improve the antifouling properties of synthesized waterborne polyurethane (WBPU) coatings, namely, WBPU-Xn and WBPU-XnAc. XnAc was synthesized by functionalization of xanthan (Xn) using polyacrylic acid. Coating hydrophilicity, adhesive strength, and erosion all varied with the Xn and XnAc contents. A moderate erosion rate was recorded only for the WBPU-XnAc coating. A good antifouling property for longer time was found in the WBPU-XnAc coating using zinc pyrithione as a biocide in the field test.

Biocompatible hydrophilic brushite coatings on AZX310 and AM50 alloys for orthopaedic implants.

Dicalcium phosphate dihydrate (DCPD) brushite coating with flake like crystal structure for the protection of AZX310 and AM50 magnesium (Mg) alloys was prepared through chemical deposition treatment. Chemical deposition treatment was employed using Ca(NO3)2·4H2O and KH2PO4 along with subsequent heat treatment. The morphological results revealed that the brushite coating with dense and uniform structures was successfully deposited on the surface of AZX310 and AM50 alloys. The X-ray diffraction (XRD) patterns and Attenuated total reflectance infrared (ATR-IR) spectrum also revealed the confirmation of DCPD layer formation. Hydrophilic nature of the DCPD coatings was confirmed by Contact angle (CA) measurements. Moreover, electrochemical immersion and in vitro studies were evaluated to measure the corrosion performance and biocompatibility performance. The deposition of DCPD coating for HTI AM50 enables a tenfold increase in the corrosion resistance compared with AZX310. Hence the ability to offer such significant improvement in corrosion resistance for HTI AM50 was coupled with more bioactive nature of the DCPD coating is a viable approach for the development of Mg-based degradable implant materials.

Sodium alginate: A promising biopolymer for corrosion protection of API X60 high strength carbon steel in saline medium.

Sodium alginate (SA), a polysaccharide biopolymer, has been studied as an effective inhibitor against the corrosion of API X60 steel in neutral 3.5% NaCl using gravimetric and electrochemical techniques (OCP, EIS and EFM). The inhibition efficiency of the SA increased with concentration but was lower at higher temperature (70°C). Electrochemical measurements showed that the SA shifted the steel corrosion potential to more positive value and reduced the kinetics of corrosion by forming an adsorbed layer which mitigated the steel surface wetting, based on contact angle measurement. SEM-EDAX was used to confirm the inhibition of SA on API X60 steel surfaces. The SA adsorbs on the steel surface through a physisorption mechanism using its carboxylate oxygen according to UV-vis and ATR-IR measurements, respectively. This phenomena result in decreased localized pitting corrosion of the API X60 steel in 3.5% NaCl solution. Theoretical results using quantum chemical calculations and Monte Carlo simulations provide further atomic level insights into the interaction of SA with steel surface.

Promising bio-composites of polypyrrole and chitosan: Surface protective and in vitro biocompatibility performance on 316L SS implants.

Advanced biomedical materials can potentially be developed from combinations of natural biodegradable polymers and synthetic polymers. We synthesized bioactive composites based on polypyrrole/chitosan through in-situ electrochemical polymerization in oxalic acid medium. Surface characterization results revealed the influence of chitosan inclusion on polypyrrole (PPy) surface morphology. Contact angle results confirmed the enhancement in surface hydrophilicity due to the addition of chitosan into the PPy matrix. Electrochemical corrosion studies revealed that the composite coatings showed enhanced protective performance compared to pure PPy. Further, we investigated the effect of the composite coatings on the growth of MG-63 human osteoblast cells to assess their biocompatibility. Monte Carlo simulations were engaged to assess the interactions between the metal surface and composite coatings. The composite containing equal parts PPy and chitosan was found to be biocompatible; together with the corrosion protection results, the findings indicated that this bioactive coating material has potential for use in 316L SS implants.

Regulation of Fanconi anemia protein FANCD2 monoubiquitination by miR-302.

Fanconi anemia (FA) is a recessively inherited multigene disease characterized by congenital defects, progressive bone marrow failure, and heightened cancer susceptibility. Monoubiquitination of the FA pathway member FANCD2 contributes to the repair of replication stalling DNA lesions. However, cellular regulation of FANCD2 monoubiquitination remains poorly understood. In the present study, we identified the miR-302 cluster as a potential regulator of FANCD2 by bioinformatics analysis. MicroRNAs (miRNAs) are the major posttranscriptional regulators of a wide variety of biological processes, and have been implicated in a number of diseases. Expression of the exogenous miR-302 cluster (without miR-367) reduced FANCD2 monoubiquitination and nuclear foci formation. Furthermore, miR-302 cells showed extensive chromosomal breakage upon MMC treatment when compared to mock control cells. Taken together, our results suggest that overexpression of miR-302 plays a critical role in the regulation of FANCD2 monoubiquitination, resulting in characteristic defects in DNA repair within cells.