The corrosion protection of four different zinc-based sacrificial coatings alloyed with Al and Mg were investigated in 0.1 M NaCl with and without 5.10−3 M Ce (III) chloride and nitrate versus ...immersion time. The effect of Ce (III) chloride and nitrate salts were evaluated by Electrochemical Impedance Spectroscopy (EIS), potentiodynamic polarization measurements, SEM-EDS, and XRD analysis. Cerium salts showed the best effectiveness for HDG, followed by ZnAl, Zn and ZnAlMg coatings. The inhibition efficiency of Ce (III) ions was stable and higher than 82.5% for all types of substrate. Moreover, cerium chloride presented higher protection than cerium nitrate in long immersion time.
The effect of cerium salts on the cut-edge of zinc-based sacrificial coated steel was investigated by theoretical approach (based on individual polarization curves on the top surface and by Scanning ...Vibrating Electrochemical Technique (SVET). In both approaches, cerium salts increase the galvanic corrosion of zinc-based sacrificial layer coupled with steel. Furthermore, the anion parts of cerium salts exhibited a synergistic accelerated effect of galvanic activity on the cross-section. The SVET results indicated that the addition of Al, Mg alloying elements promotes localized corrosion and influences the formation and distribution of corrosion products.
•Effect of CeCl3 and Ce(NO3)3 on the cut-edge of steel coated by zinc alloyed (HDG, ZnAl, and ZAM).•Cerium salts accelerated the corrosion of zinc coated steel on the cut-edge.•NO3- ion exhibited a synergistic accelerating effect on galvanic corrosion.•The presence of Al and Mg alloying elements promotes localized corrosion.
A synthetic method for isoquinoline synthesis via a 4+2 annulation of NH imines with alkynes using the high‐valent (pentamethylcyclopentadienyl)cobalt(III) Cp*Co(III) catalyst is described. ...Cerium(IV) sulfate was found to be an efficient oxidant in lieu of the commonly used copper or silver salts. Broad substrate scope, high functional group tolerance, and generally good yields were observed.
•Cerium modified montmorillonite (CeMMT) is an efficient corrosion inhibitor for AA2024.•60 wt.% of cerium ions are released in 0.1 M NaCl from modified nanoclays.•CeMMT improves the barrier ...properties of the doped sol–gel film applied on AA2024.•Cerium ions provide an active corrosion protection to the doped sol–gel film.
This work presents a new approach to develop protective pre-treatment for AA2024 based on the inhibitor efficiency of cerium ions which are considered as a promising alternative to replace chromate compounds. The inhibition properties of cerium salts for improving the anti-corrosion performance of AA2024 have been characterized by polarization curves and EIS measurements. Cerium ions were inserted into nanoclays platelets by cationic-exchange reactions (CeMMT). XRD analysis proved the presence of cerium ions intercalated into clay structure. EIS measurements and polarization curves highlighted a high corrosion inhibition effect of cerium-modified nanoclays. This effectiveness can be related to the release of 60% of cerium ions from CeMMT structure in sodium chloride as determined by UV–vis measurements. Salt spray test made on scratched sol–gel samples indicated a self-healing effect of cerium ions which provide an active corrosion protection to aluminum substrate. EIS measurements revealed that hybrid sol–gel films doped with CeMMT improve barrier properties and anticorrosion protection of aluminum 2024 substrate.
The stratum corneum protects the body against external agents, such as metals, chemicals, and toxics. Although it is considered poorly permeable to them, comprising the major barrier to the ...permeation of such substances, it may become a relevant gate of entry for such molecules. Cerium (Ce) is a lanthanide that is widely used in catalytic, energy, biological and medicinal applications, owing to its intrinsic structural and unique redox properties. Cerium salts used to produce cerium oxide (CeO2) nanostructures can potentially come into contact with the skin and be absorbed following dermal exposure. The objective of this study was to investigate the percutaneous absorption of three inorganic Ce salts: cerium (III) chloride (CeCl3); cerium (III) nitrate (Ce(NO3)3) and ammonium cerium (IV) nitrate (Ce(NH4)2(NO3)6), which are commonly adopted for the synthesis of CeO2 using in vitro - ex vivo technique in Franz diffusion cells. The present work shows that Ce salts cannot permeate intact human skin, but they can penetrate significantly in the epidermis (up to 0.29 μg/cm2) and, to a lesser extent in dermis (up to 0.11 μg/cm2). Further studies are required to evaluate the potential effects of long-term exposure to Ce.
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•Skin may be an entry route of xenobiotics inducing local effects.•Human skin permeation of inorganic Cerium (Ce) salts was negligible.•No potential risk of Ce to reach the systemic circulation.
Recently, nanobiotechnology has been developing intensively; therefore, various properties of nanoparticles, which depend on their origin, concentration, and size, are of interest. It is known that ...CeO2 nanoparticles cause a positive biological effect. These particles are able to penetrate through biomembranes. At the same time, there are assumptions about a high degree of biological risks when using nanomaterials, and it is obvious that the biosafety of nanomaterials is decisive in the
development of new products, including for medicine. The cytotoxicity of samples of cerium salts and cerium dioxide nanoparticles of different sizes was assessed at different concentrations using D. viridis. The cytotoxicity level by morphological and functional disorders of D. viridis was investigated, as determined by the change in cell shape, accumulation of inclusions, loss of flagellum, change in nature and movement, the formation of micro- and macroaggregates by D. viridis cells and exometabolite release. The cytotoxicity coefficient was calculated as a quotient of total detected changes divided by their number. It was shown that cerium salts (cerium (IV) ammonium nitrate and cerium (III) chloride) had pronounced cytotoxicity,
which exceeded cytotoxicity values of the control by 7 and 6 times, respectively.
The possibility that various chemical treatments may enhance the corrosion resistance of a magnesium alloy (containing rare earths, WE43 alloy) has been investigated. Cerium(III) conversion coatings ...and silanic coatings, with and without acid pickling, were tested in 0.1 N Na
2SO
4 solution. Silanic coatings were obtained by dipping WE43 specimens in diluted hydroalcoholic silanic solutions and successively cured at 100 °C for 1 h.
A silanic compound with a long aliphatic chain (e.g.
n-octadecyltrimethoxysilane, OctadecS) produced a very protective and relatively persistent coating, while that with a mercapto group (3-mercapto-propyl-trimethoxysilane, PropS–SH) formed less protective layers. Treatments with cerium salts (cerium(III) sulphate or cerium(III) chloride
+
hydrogen peroxide) did not produce encouraging results. Under no conditions did acid pickling improve the performance of the coatings.
Cerium conversion coatings were explored as an alternative to chromate conversion coatings for corrosion protection of aluminium alloy 7075-T6. Conversion coatings were formed in a conversion bath of ...0.05 M cerium salt and 0.25 M hydrogen peroxide at room temperature. Various cerium salts were used: Ce(III) acetate, Ce(III) nitrate and Ce(III) chloride. The conversion process from Ce.sup.3+ to Ce.sup.4+ was followed by UV-VIS spectroscopy. The conversion of cerium coatings on alloy surface was monitored by measuring open circuit potential. To investigate the corrosion properties of uncoated and coated samples, the linear polarization and electrochemical potentiodynamic curves were recorded in 0.1 M NaCl. Additionally, salt spray chamber testing was carried out. Samples were characterized by scanning electron microscopy. Results revealed that the cerium conversion and corrosion resistance were dependent on the type of cerium salt and conversion time in the conversion bath. The most compact and uniform cerium conversion coatings were produced from solution of cerium(III) acetate, but better protection was obtained in nitrate and, especially, chloride solutions due to thicker coatings. Keywords: aluminium alloy 7075-T6, corrosion, cerium conversion coatings, cerium salts
The present work examines the effects of cerium salts on corrosion behaviors of Si-Zr hybrid sol-gel coatings. The Si-Zr hybrid sol-gel coatings on a 2A l2 aluminum substrate were pre- pared through ...hydrolysis and condensation of glycidoxypropyl-trimethoxy-silane （GTMS） and zirconium（IV） n-propoxide （TPOZ）. Used as inhibitors for corrosion, three types of cerium salts （Co（NO3）3, CeCl3, and Ce（CH3COO）3） were doped into the sol-gel coatings. Fourier transform infrared （FTIR） and scanning electron microscopy （SEM） were employed to investigate the structures and morphologies of various coatings, and the corrosion resistances of the coatings were evaluated by electrochemical methods and neutral salt spray tests. Experimental results indicate that the addition of cerium salts can hinder the process of corrosion due to their self-healing abili- ties. Furthermore, the sol-gel coating doped with Ce（CH3COO）3 has the best corrosion resistance because of the promotions of hydrolysis and condensation provided by CH3COO-.
The oxidative free radical reactions between 2-amino-1,4-naphthoquinones and β-dicarbonyl compounds mediated by cerium(IV) salts are described. In contrast to those mediated by manganese(III) ...acetate, the cerium(IV) mediated free radical reaction provides a novel method for the synthesis of benzo
findole-4,9-diones exclusively. This high selectivity is due to the strong oxaphilicity of the cerium salts.
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