Cyclic Salts Research Articles

In-situ monitoring of the corrosion behaviour of austempered ductile iron (ADI) under cyclic salt spray exposure

The corrosion behavior of austempered ductile iron (ADI) under cyclic salt spray exposure was studied using a specific three-electrode cell located in the salt fog chamber. Three steps were identified, namely pitting corrosion of ferrite (very first cycles), followed by inward oxidation of the ausferrite matrix and then (iii) mixed oxidation of the matrix associated with the formation of a rust layer at the specimen surface. Evolution of the corrosion rate calculated from in-situ electrochemical measurements was correlated with surface changes quantified from optical and field emission scanning electron (FE-SEM/EDS) microscopies. Corrosion products were identified by means of micro-Raman spectroscopy.

Discovery of Novel Cyclic Salt Bridge in Thermophilic Bacterial Protease and Study of its Sequence and Structure.

The plausible explanation behind the stability of thermophilic protein is still yet to be defined more clearly. Here, an in silico study has been undertaken by investigating the sequence and structure of protease from thermophilic (tPro) bacteria and mesophilic (mPro) bacteria. Results showed that charged and uncharged polar residues have higher abundance in tPro. In extreme environment, the tPro is stabilized by high number of isolated and network salt bridges. A novel cyclic salt bridge is also found in a structure of tPro. High number of metal ion-binding site also helps in protein stabilization of thermophilic protease. Aromatic-aromatic interactions also play a crucial role in tPro stabilization. Formation of long network aromatic-aromatic interactions also first time reported here. Finally, the present study provides a major insight with a newly identified cyclic salt bridge in the stability of the enzyme, which may be helpful for protein engineering. It is also used in industrial applications for human welfare.

Structural insights into kinetoplastid coronin oligomerization domain and F-actin interaction.

The two-domain actin associated protein coronin interacts with filamentous (F-) actin, facilitating diverse biological processes including cell proliferation, motility, phagocytosis, host-parasite interaction and cargo binding. The conserved N-terminal β-propeller domain is involved in protein: protein interactions, while the C-terminal coiled-coil domain mediates oligomerization, transducing conformational changes. The L. donovani coronin coiled-coil (LdCoroCC) domain exhibited a novel topology and oligomer association with an inherent asymmetry, caused primarily by three a residues of successive heptads. In the T.brucei homolog (TbrCoro), two of these ‘a’ residues are different (Val 493 & 507 replacing LdCoroCC Ile 486 and Met 500 respectively). The elucidated structure possesses a similar topology and assembly while comparative structural analysis shows that the T.brucei coronin coiled-coil domain (TbrCoroCC) too possesses the asymmetry though its magnitude is smaller. Analysis identifies that the asymmetric state is stabilized via cyclic salt bridges formed by Arg 497 and Glu 504. Co-localization studies (LdCoro, TbrCoro and corresponding mutant coiled coil constructs) with actin show that there are subtle differences in their binding patterns, with the double mutant V493I–V507M showing maximal effect. None of the constructs have an effect on F-actin length. Taken together with LdCoroCC, we therefore conclude that the inherent asymmetric structures are essential for kinetoplastids, and are of interest in understanding and exploiting actin dynamics.

Intramolecular Cycloaddition of [3-(Naphthalen-1-yl)prop-2-yn-1-yl](3-phenylprop-2-en-1-yl)ammonium Bromides and Cleavage of Some of the Obtained Cyclic Salts in Aqueous Alkali

Intramolecular cycloaddition of [3-(naphthalen-1-yl)prop-2-yn-1-yl](3-phenylprop-2-en-1-yl)ammonium bromide under very mild conditions afforded potentially biologically active 4-phenyl-3a,4-dihydronaphtho[f]isoindolium salts in high yields. Some of the synthesized salts underwent cleavage on heating in aqueous alkali to give mixtures of isomeric aminomethylphenanthrenes.

Heterocyclization of amino alcohols into saturated cyclic quaternary ammonium salts

Cyclodehydration of available N-alkylethanolamines with aldehydes and simultaneous or subsequent quaternization afford functionalized quaternary ammonium salts of N-nitroimidazolidine, oxazolidine and annulated bismorpholine type. Further replacement of their anions with residues of explosive acids provides a series of energyintensive quaternary salts with a rich hydrogen content possessing satisfactory energy characteristics and sufficiently high thermal stability.

Durability and mechanical behavior of CFRP/Al structural joints in accelerated cyclic corrosion environments

This study aims to evaluate detailed corrosion characteristics and mechanical performance of CFRP/Al bonded and hybrid bonded-riveted joints subjected to cyclic salt mist-dry-wet environments. Results indicated that joint strength of both bonded and hybrid joints progressively declined with increased ageing cycles with up to 40.4% and 31.9% degradation, respectively. Compared with purely bonded joints, hybrid joints presented superior mechanical properties and less degradation rate. Light fiber tearing failure and cohesive failure predominated for less aged joints, while more apparent interface failure and accumulated corrosion products were observed at higher ageing cycles. The main corrosion mechanism was the pitting corrosion on the aluminum substrate surface, which further led to the formation of accumulated corrosion products and disbonding of the aluminum/adhesive interface. Rivet body of hybrid joints remained pristine and rivet heads experienced severe galvanic corrosion, while these corrosion features generated limited impact on joint performance.

ALKYLATION OF IMIDAZOLE AND BENZOTRIAZOLE DERIVATIVES BY 1,3-DIIODOPROPAN-2-ONE IN THE ABSENCE OF A BASE

The reaction of imidazole and benzotriazole derivatives with 1,3-diiodopropan-2-one in the absence of bases and catalysts leads to the formation of linear and cyclic salt systems in one preparative step. Authors: Larisa V. Zhilitskaya*, Ludmila G. Shagun, Ivan А. Dorofeev, Nina O. Yarosh

Alkylation of imidazole and benzotriazole derivatives by 1,3-diiodopropan-2-one in the absence of a base

The reaction of imidazole and benzotriazole derivatives with 1,3-diiodopropan-2-one in the absence of bases and catalysts leads to the formation of linear and cyclic salt systems in one preparative step.

Corrosion behavior of the joints of carbon fiber reinforced polymers with DP590 steel and Al6022 alloy

Purpose This study aims to propose a simple experimental method to distinguish the galvanic corrosion, crevice corrosion and self-corrosion in metal/carbon fiber reinforced polymer (CFRP) joints. Design/methodology/approach The corrosion behaviors of four different galvanic couples, whose anodes were Zn-coated DP590 steel and Al 6022, and cathodes were two kinds of CFRP, were investigated in immersion and GMW14872 cyclic conditions. Findings The results showed that the galvanic corrosion caused by direct contact between CFRP and metals was more serious than that caused by the jointing bolts. The corrosion damage caused by crevice corrosion was severer than that caused by galvanic corrosion. Self-corrosion was also significant, particularly under the cyclic salt spray condition. Practical implications Cyclic salt spray test may more reliably simulate the galvanic corrosion of a joint in industrial service environments, and real corrosion damage may be underestimated by a galvanic current measurement. Originality/value A deeper understanding of different corrosion mechanisms involved in CFRP/metal joints under different service conditions in industry has been given.

Axially Chiral Biaryl Compounds via Cu-Catalyzed Acyloxylations of Cyclic Diaryliodonium Salts

Axially Chiral Biaryl Compounds via Cu-Catalyzed Acyloxylations of Cyclic Diaryliodonium Salts

Model for the Patterns of Salt-Spray-Induced Chloride Corrosion in Concretes under Coupling Action of Cyclic Loading and Salt Spray Corrosion

In this study, the patterns of chloride ion erosion of unsaturated concrete subjected to the coupling action of cyclic loading and salt spray corrosion were experimentally studied, and Fick’s Second Law was used to fit the variation patterns of chloride concentration to obtain the chloride diffusion coefficient. Accordingly, we have established a mathematical model that describes chloride transport in unsaturated concrete and accounts for the effects of gas flow, water migration, convection diffusion, and capillary action. This model is composed of three equations—the gas flow equation, the solution flow equation, and the solute convection–diffusion equation. The COMSOL numerical analysis software was subsequently used to obtain solutions for this model, based on parameters such as porosity and the chloride diffusion coefficient. Subsequently, the saturation, relative permeability, and the chloride ion concentration during the first corrosion cycle were analyzed. The numerical results were consistent with the experimental values and were therefore superior to the values obtained using Fick’s Second Law.

The preparation and application of optically active organophosphorus compounds

Racemic acyclic phosphine oxides were separated into their enantiomers applying classical resolution methods based on complexation with chiral host molecules. The preparation of chloro-3-phospholenium chlorides was elaborated by the reaction of 3-phospholene oxides with oxalyl chloride. The cyclic chlorophosphonium salts were key intermediates, as they could be converted to the corresponding 3-phospholene boranes. Moreover, these reactive intermediates could be reacted with chiral alcohols, which enabled us to develop a dynamic resolution of 3-phospholene oxides based on the formation of covalent diastereomeric intermediates. P-Stereogenic phosphine oxide pre-catalysts showed promising enantioselectivity values in a catalytic Wittig-reaction.

Biochemical and growth responses of silver maple (Acer saccharinum L.) to sodium chloride and calcium chloride.

The present research investigated the response of silver maple (Acer saccharinum L.) to salt treatment. The short- and long-term effects of NaCl and CaCl2 treatments on plant fitness characteristics (growth parameters, leaf chlorophyll content) and biochemical stress-coping mechanisms (proline accumulation as well as enzymatic activities) were examined. We found that the silver maple response to salt stress strictly depended on salt type and dose—calcium chloride was less toxic than sodium chloride, but high concentrations of both salts negatively influenced plant growth. The accumulation of proline, slight changes in the activity of superoxide dismutase and marked changes in catalase and peroxidase activities in the roots and leaves indicated complexity of the plant response. It was also shown that after one year, enzymatic parameters were restabilized, which indicates plant recovery, but the reduced mass of seedlings suggests that one year is not enough to cope with the prolonged cyclic salt stress, both resulting from NaCl and CaCl2 application. Therefore, seedlings of silver maple should be considered as moderately susceptible to salinity. Hence, it is recommended to use silver maple on non-de-iced urban areas, while planting on often de-iced roads should be avoided.

Influence of Salt Fog Test on Silicone Rubber Insulating Material Under AC and DC Voltages

The present work investigates the performance of electrically stressed silicone rubber insulating material in a cyclic salt fog test. Corona Inception Voltage due to water droplet initiated discharges changes after salt fog ageing. The Ultra High Frequency signals radiated during corona discharge activity under AC voltages have a frequency span of 0.8–1.5 GHz, whereas under DC voltages span lies in the range of 0.5–1.5 GHz. Contact angle reduces with the increase in number of salt fog ageing cycles. Surface potential accumulation studies indicate that salt fog aged silicone rubber shows characteristic variation in accumulated potential magnitude and the decay characteristics. Further tdv/dt of surface potential decay characteristics enables to understand the charge penetration depth. Weight loss studies and surface roughness analysis during salt fog test are used to quantify the amount of damage.

Electrochemical impedance spectroscopy of scribed coated steel after salt spray testing

In the present study, various representative models of finite length diffusion impedance were examined, in order to find the optimum description for dissolved oxygen diffusion, during corrosion of scribed coated steel in cyclic salt spray conditions, at 6, 8 and 12-week intervals. Modified restricted diffusion fitted the experimental data after 6 and 8 weeks and modified restricted or modified transmissive could fit the data after 12 weeks, accompanied by a decrease in corrosion resistance. Oxygen would diffuse through the porous corrosion layer and reduce on the magnetite layer, lying on top of the electrode surface.

Corrosion Resistance of Copper Coatings Deposited by Cold Spraying

In the article, a study of corrosion resistance of copper and copper-based cermet (Cu+Al2O3 and Cu+SiC) coatings deposited onto aluminum alloy substrate using the low-pressure cold spraying method is presented. The samples were subjected to two different corrosion tests at room temperature: (1) Kesternich test and (2) a cyclic salt spray test. The selected tests were allowed to simulate service conditions typical for urban, industrial and marine environment. Examination of corroded samples included analysis changes on the coating surface and in the microstructure. The physicochemical tests were carried out using x-ray diffraction to define corrosion products. Moreover, microhardness and electrical conductivity measurements were conducted to estimate mechanical and physical properties of the coatings after corrosion tests. XRD analysis clearly showed that regardless of corrosion conditions, for all samples cuprite (Cu2O) was the main product. However, in the case of Cu+Al2O3 cermet coating, chlorine- and sulfate-containing phases such as Cu2Cl(OH)3 (paracetamite) and Cu3(SO4)(OH)4 (antlerite) were also recorded. This observation gives better understanding of the lowest microstructure changes observed for Cu+Al2O3 coating after the corrosion tests. This is also a justification for the lowest decrease in electrical conductivity registered after the corrosion tests for this coating.

Rust morphology characterization of polyurethane and acrylic-based marine antifouling paints after salt spray test on scribed specimens

A newly developed, polyurethane-based, marine antifouling coating, containing 2% immobilized Econea, was examined in terms of its anticorrosion performance. The novelty of the experimental formulation arises from the immobilization of the biocide which minimizes leaching and was accomplished via a newly developed functionalization method, based on reaction of the biocide with highly reactive isocyanate functionality. The painting system was applied on steel specimens, then scribed with a sharp cutter and examined for 12 weeks in cyclic salt spray exposure. Identification of the rust morphologies was performed with XRD, Raman spectroscopy, SEM, and EDS methods. The absence of paint deformation during the experiment led to the formation of compact corrosion products, firmly adherent to the substrate, allowing transformation to more protective forms, such as oxides (hematite, maghemite, magnetite) and the least harmful of the oxyhydroxides (goethite, feroxyhyte), found in the mixture, ensuring sufficient corrosion protection. The unscratched part of the paint served as a barrier to corrosion product expansion beyond the scribed areas. An acrylic-based antifouling system was also examined for reasons of comparison. The experimental formulation exhibited superior anticorrosion performance overall, since the acrylic system presented extended material loss, blistering, checking, and extensive substrate rust coverage beneath the multilayer coat, implying unsatisfactory corrosion protection.

Microstructure and Corrosion Resistance of Aluminium and Copper Composite Coatings Deposited by LPCS Method

Abstract The paper presents the study of microstructure and corrosion resistance of composite coatings (Al+Al2O3 and Cu+Al2O3) deposited by Low Pressure Cold Spraying method (LPCS). The atmospheric corrosion resistance was examined by subjecting the samples to cyclic salt spray and Kesternich test chambers, with NaCl and SO2 atmospheres, respectively. The selected tests allowed reflecting the actual working conditions of the coatings. The analysis showed very satisfactory results for copper coatings. After eighteen cycles, with a total time of 432 hours, the samples show little signs of corrosion. Due to their greater susceptibility to chloride ions, aluminium coatings have significant corrosion losses.

Rust morphology characterization of silicone-based marine antifouling paints after salt spray test on scribed specimens

A newly developed, silicone-based, marine antifouling coating, containing 0.56% immobilized Econea, was examined in terms of its anticorrosion performance. The novelty of the experimental formulation arises from the immobilization of the biocide which minimizes leaching and was accomplished via a newly developed functionalization method, based on reaction of the biocide with highly reactive isocyanate functionality. The painting system was applied on steel specimens, then scribed with a sharp cutter and examined for 12 weeks in cyclic salt spray exposure. Identification of the rust morphologies was done with XRD, Raman spectroscopy, SEM and EDS methods. The observed paint swelling during the experiment caused the formation of large, coarse rust agglomerates without adherence, which detached frequently causing reinitiation of the corrosion process. This procedure was revealed by the oxyhydroxide nature of the corrosion products. The basic corrosion morphology observed was a mixture of akaganeite and goethite. A commercial, silicone-based, foul-release coating served as a reference. The experimental formulation exhibited superior anticorrosion performance overall, since the reference system presented higher enlargement of the scribed areas, increased substrate material loss, a highly inhomogeneous corrosion layer with voids and smaller (stable) goethite amounts in the rust areas containing mainly akaganeite/goethite mixture.

Corrosion resistance of tin coatings deposited by cold spraying

This article presents a study of corrosion resistance of tin and tin-based composite (Sn + Al2O3 and Sn + SiC) coatings deposited onto aluminium alloy substrates using the low-pressure cold spraying method. The samples were subjected to three different corrosion tests at a room temperature: (i) Kesternich test, (ii) a cyclic salt spray test and (iii) anodic polarisation test. The selected tests allowed extreme environment simulation typical for wide range of urban, industrial and marine service conditions. Evaluation of corrosion was carried out by analysing changes on the coating surface as well as in the microstructure. Additionally, the physicochemical tests were carried out using X-ray diffraction. XRD analysis clearly showed that abhurite Sn21O6Cl16(OH)14 is the main corrosion product established after the polarisation measurements. Despite extreme corrosive conditions used in experiments all tin coatings showed minor corrosion changes which implies that abhurite serves as a buffer between the metal and the oxidising natural environment.