Longer Immersion Research Articles

Corrosion protection properties of inhibitor containing hybrid PEO-epoxy coating on magnesium

A hybrid PEO-epoxy coating was developed for magnesium. A highly-efficient corrosion inhibitor (3-methysalicylate) was impregnated into the anodized layer, which was sealed by an epoxy layer through dip-coating process. Influence of dip-coating parameters on coating properties was investigated. The corrosion performance was evaluated through general and localized electrochemical techniques. As a result, the epoxy layers registered superior resistance, whereas the anodized layer suppressed corrosion expansion. Longer immersion and triple-dipping favored the production of better sealed epoxy layer. The active protection mechanism was achieved by suppression the re-deposition of detrimental impurity and/or adsorption upon the exposed surface from incorporated inhibitor.

Influence of Early-Stage Hydrolysis on Tensile Fracture Behavior of HAp/PLA Composites Interface-Controlled by Reaction Control Utilizing Photodissociable Protecting Groups

In this study, the change in the tensile fracture behavior of HAp/PLA composites, interface-controlled using pectin and chitosan, was evaluated for the case of the early-stage hydrolysis. Here, the reaction between the HAp particles and modification polymers was controlled using o-nitrobenzyl alcohol. Tensile tests after immersion in a pseudo biological environment indicated that the interface-control method employed in this study improved the fracture properties of HAp/PLA composites significantly, inducing the large plastic deformation. In addition, the effects of early-stage hydrolysis on fracture behavior and mechanism are discussed from the viewpoint of interfacial structures for the interface-controlled HAp/PLA composites. Observations of fracture morphologies and surfaces suggest that the interface-control employed in this study successfully improved interfacial bonding, enabling the effective usage of the deformability of the PLA matrix. The interface-control method employed in this study also maximized the fracture strain through the combination of improved interfacial bonding and an increase in the ductility of the PLA matrix after a 2-week immersion. Test results also suggest that the cancelation induced by the degradation of chitosan accelerated the degradation of the PLA matrix after a longer immersion.

Spectroscopic properties of triangular silver nanoplates immobilized on polyelectrolyte multilayer-modified glass substrates

Fabrication of surface-immobilized silver nanostructures with reproducible plasmonic properties by dip-coating technique is difficult due to shape alteration. To address this challenge, we used a polyelectrolyte multilayer to promote immobilization of as-received triangular silver nanoplates (TSNP) on a glass substrate through electrostatic interaction. The substrate-immobilized TSNP were characterized by absorption spectrophotometry and scanning electron microscopy. The bandwidth and peak position of localized surface plasmon resonance (LSPR) bands can be tuned by simply varying the concentration of the colloidal solution and immersion time. TSNP immobilized from a higher concentration of colloidal solution with longer immersion time produced broadened LSPR bands in the near-IR region, while a lower concentration with shorter immersion time produced narrower bands in the visible region. The shape of the nanoplates was retained even at long immersion time. Analysis of peak positions and bandwidths also revealed the point at which the main species of the immobilization had been changed from isolates to aggregates.

Pengaruh Perendaman Pada Saliva Buatan Selama 14 Hari Pada Glass Fiber Non Dental Dan Glass Fiber Dental Terhadap Perlekatan Bakteri Streptococcus Mutans

The material in the oral cavity will be coated by saliva. The humidity of material that is immersed in water will increase from time to time. Longer immersion time in water causes an increase in the absorption of water by a material. Non-dental glass fiber can be used as an alternative replacement for fiber glass dental. The advantages of dental glass fiberis widely available with reasonably priced. Fiber glass non dental commonly used as building materials and automotive. Streptococcus mutans bacteria have the ability to stick to the whole surface of the mouth, including dental materials. The purpose of this study is to determine the effect of dental glass fiber and non-dental glass fiber immersion in artificial saliva for 14 days to the adhesions of Streptococcus mutans bacteria.Fiber used in this study is E-glass fiber dental(Fibersplint, Polydentia SA, Switzerland), non-dental glass fiber A (LT, China), flowable composite (CharmFil Flow, Denkist, Korea) and silane coupling agent (Monobond S, Ivoclar Vivadent, Liechtenstein). Subjects were divided into three groups, each group consisting of 5 samples. Streptococcus mutans bacteria was planted in BHI media and calculated by plate count method. Results were analyzed using ANAVA. From the research it showed that the average dental glass fiber bacterial adhesions value was (953.4 ± 7.19), non-dental glass fiber(953.4 ± 7.19) while the composite resin without using fiber glass (848 ± 7.07). Statistical analysis showed a variable composition have a significant effect (p <0.05). The conclusion of this research that the alkali metal content in the fiber glass can affect the amount of bacteria Streptococcus mutans adhesions.

Corrosion resistance of Al and Al–Mn thin films

Magnetron-sputtered aluminum (Al) and aluminum–manganese (Al-Mn) films with structures ranging from nanocrystalline to amorphous were obtained by tuning the Mn% up to 20.5at.%. Corrosion behavior of the films was investigated in 0.6M and 0.01M NaCl aqueous solutions by potentiodynamic polarization and electrochemical impedance spectroscopy. Pitting corrosion was found to be strongly affected by alloy composition. The amorphous Al–20.5at.% Mn exhibited the best pitting resistance during short term exposure. However, over longer immersion in 0.01M NaCl up to 108h, nanocrystalline Al–5.2at.% Mn showed the highest corrosion resistance. The dual-phase Al-11.5at.% Mn alloy was found to have higher nominal corrosion rate compared to its nanocrystalline or amorphous counterparts.

The effect of counter cation species on the formation of various crystal forms and their phase transition behavior of poly(vinyl alcohol)-iodine complex

Poly(vinyl alcohol) [PVA, -(CH2CH(OH))n-] forms the crystalline complexes I and II with iodine ions (I3−) when PVA is immersed in the KI/I2 aqueous solutions of 0.1–0.5 and 1–3 mol/l concentration, respectively. On the basis of the X-ray diffraction and the ultraviolet-visible, IR and Raman spectral data, we have found that the immersion of PVA films into the iodine aqueous solutions containing the different type of counter ions (K+, Na+, Li+, H+, or Cs+) creates the various types of the crystal modification. When PVA sample was immersed in the solution of relatively low concentration, all the types of counter ion gave the complex I structure. When the concentration of the solution was increased to 1–3 mol/l, the sample immersed for several hours showed the formation of the complex II. In the case of H+ ion, the longer immersion was found to give a new crystal form or complex III with the different packing mode of PVA and I3− ions as determined by the X-ray structure analysis. In the cases of Na+ and Li+ ions, the complex II was disordered by the longer immersion in such a highly-concentrated solution. As clarified by the infrared spectral data, the hydrogen bonds of O–H ⋯ I type are formed in the iodine complex, the strength of which was found also to be different depending on the type of counter ion species. In this way, the present paper has revealed the important role of the counter cations on the formation and stability of the PVA-iodine complexes for the first time.

Relationship between tissue phosphorus and seawater phosphate in the brown alga Hormosira banksii

We measured tissue phosphorus content of high and low intertidal Hormosira banksii to test the hypothesis that tissue phosphorus content would be greater in individuals from the low intertidal because of greater total uptake associated with longer immersion in seawater. Moreover, we predicted that tissue phosphorus would be greater at sites where the seawater contained higher phosphate concentrations. There was a positive, linear relationship between local seawater phosphate concentrations and tissue phosphorus content of H. banksii from high and low intertidal zones at six different sites in winter. However, there were no comparable relationships in summer, even though the range of seawater phosphate concentration was similar in both seasons. The phosphorus contents of low intertidal H. banksii were significantly greater than high intertidal H. banksii in winter, but not in summer. Reasons for these differences may be related to greater access to seawater phosphate in low intertidal algae (than those in the high intertidal) in winter, followed by greater utilisation of the internal phosphorus between winter and summer, due to faster growth rates in the low intertidal.

Effect of Electrochemical Cell Design on the Ionic Conductivity and Oxygen Permeability Determination of Gas Separators

Electrochemical properties of gas separators, holding a potential for the application in alkaline electrolysis, such as ionic conductivity and impermeability for hydrogen and oxygen gases, are significantly influencing the efficiency of alkaline electrolysis. Both non-zero gap and zero gap atmospheric pressure laboratory scale test set-up, operating at room temperature, were developed in order to undertake a comparative study of their advantages and disadvantages for the lab scale electrochemical characterization of gas separator materials. The zero gap cell was able to provide a more accurate ionic conductivity of the separators via Electrochemical Impedance Spectroscopy (EIS). The non-zero gap cell set-up, coupled with Quadrupole Mass Spectrometer (QMS), enabled the quantitative assessment of the oxygen crossover of different separators. The influence of a long term immersion in 25wt. % KOH determined using the non-zero gap cell, showed increased conductivity with immersion duration for asbestos, while the highly hydrophobic PPS and PPS with PTFE separators’ conductivity was not affected by longer immersion.

Precise drop dispensation on superhydrophobic surfaces using acoustic nebulization

The adhesion forces of liquid drops on superhydrophobic surfaces are typically in the nano-Newton range which presents problems in their dispensation from pipettes. Furthermore, since the liquid adheres more strongly to the pipette tip, some portion of the liquid will tend to remain on the tip, causing inaccuracy in the volume dispensed. We advance a novel approach here, in which the spray from an acoustic nebulizer is sent to a superhydrophobic receptacle and the volume ascertained precisely using a weighing scale. The superhydrophobic surface was identified to develop via a galvanic displacement mechanism in an electroless deposition process. A time dependent morphology change from granular to dendritic with longer immersion into the silver nitrate solution was found which indicated that granular growth beyond a certain size was not feasible, although granular structures were more preferentially formed just after nucleation. The dendritic structure formation was likely due to the natural tendency of the process to maintain or increase the surface area to volume ratio in order not to limit the rate of deposition. An immersion for at least 7 seconds into the silver nitrate solution, when the granular structures were predominant, was all that was needed to ensure superhydrophobicity of the surfaces. Also, the superhydrophobic state required not just significant numbers of the granular structures to be present but also interrupted coverage on the surface. On using the technique, a single drop was created by subsequently covering the receptacle with a lid and shaking it gently. The volume dispensed was found to vary linearly with the operation time of the nebulizer. We elucidated the observed increased ability of drops to reside on inclines using wetting mechanics and presented an elementary mathematical description of the extent of aerosol coverage on the surface, which has implications for the mechanics of aerosol growth into drops. The structural changes in enhanced green fluorescent protein (EGFP) observed after acoustic dispensation necessitated all samples in a fluorimetric assay to involve equal nebulized volumes of the fluorescent protein marker for measurement consistency.

On corrosion behaviour of magnesium alloy AZ31 in simulated body fluids and influence of ionic liquid pretreatments

This paper reports on the corrosion of Mg alloy AZ31 in simulated body fluid (SBF) using static immersion tests and electrochemical impedance spectroscopy. A preliminary study on the effect of flowing SBF on the corrosion behaviour of AZ31 has also been carried out. Low toxicity ionic liquids (ILs) trimethyl(butyl)phosphonium diphenyl phosphate P1444DPP and trihexyl(tetradecyl)phosphonium bis-2,4,4trimethylpentyl-phosphinate [P66614][i(C8)2PO2] have been used to provide corrosion protection for AZ31 in SBF. Time dependent immersion tests indicate that under static conditions, AZ31 suffers severe localised corrosion in SBF, with pits developing predominantly beside the Al–Mn intermetallic phase in the α matrix. At longer immersion times, the corrosion product eventually precipitates and covers the entire specimen surface. When exposed to SBF under flowing conditions with a shear stress of 0·88 Pa, more uniform corrosion was observed. The optical profilometry results and electrochemical impedance spectroscopy analysis suggest that both P1444DPP and [P66614][i(C8)2PO2] pretreatments can increase the corrosion resistance of AZ31 in SBF, in particular by decreasing the number of deeper pits found on the alloy surface. Cytotoxic test shows that the presence of the ILs P1444DPP and [P66614][i(C8)2PO2] in cell culture media slightly inhibits the growth of human coronary artery endothelial cells in comparison with the good cell viability around the treated specimen. A pretreatment with IL is used in order to improve the corrosion resistance of this alloy in SBF.

The Rehealing Ability of Oxide Scales on K52 Nanocrystalline Coating after Pitting Corrosion

The rehealing ability of the oxide scales on sputter-deposited Ni-based K52 nanocrystalline coatings after pitting corrosion had been studied by polarization curves in 3.5% NaCl solution. The results indicated that the oxide scales formed on the nano-coatings exhibited excellent rehealing ability after pitting corrosion, and the rehealing oxide scales still had high corrosion resistance. The rehealing ability was declined with longer immersion time in the chloride solution. EDX analyses revealed that the oxide scales within the pits were composed of mixed-oxides. The mixed-oxides were made up of two layers: the external oxide layer was composed of Cr2O3 and TiO2 and the internal oxide layer was Al2O3.

Corrosion of N80 tubing steel in brine at 1·2 MPa CO2 containing trace amounts of H2S

The corrosion of N80 tubing steel was measured electrochemically in an autoclave at an overall carbon dioxide pressure of 1·2 MPa. Both potentiodynamic polarisation curves and electrochemical impedance data were analysed to obtain the relevant kinetic parameters. The influences of H2S pressure and immersion time on the corrosion of N80 were analysed in detail. The results indicate that protective sulphide scales may form at higher partial pressures of H2S and greatly decreased the corrosion rate of N80 steel as the immersion time increased. Thus, the capacitive loop shrinks gradually in the low frequency region and eventually shifts to a single capacitive loop at low H2S concentration, whereas at higher H2S concentrations, the capacitive loop gradually disappeared, and diffusion controlled processes then predominated owing to the formation of a protective corrosion scale at longer immersion times.

Improved soiling resistance of polypropylene fibers on the addition of synthetic compounds

With the aim of enhancing the soil resistance of polypropylene (PP) fibers, polydimethylsiloxane (PDMS) and/or oleamide (OA) were added, and the soiling and wear resistances of the obtained fibers were evaluated. Films made from PP with the addition of PDMS and/or OA were fabricated and their water repellencies were evaluated by using droplets to measure their contact angles. The water contact angle increased with increasing amount of PDMS and/or OA added to PP. These blended resins were then used to produce fibers, which were in turn used to form fabrics. The soil resistances of these fabrics were evaluated by immersing them in aqueous solutions of a water-soluble artificial soiling substance for 1 min. Fiber G, for which both PDMS and OA had been added to PP, had a soiling ratio that was about 8–15% lower than that of pure PP fibers to which nothing had been added. Longer immersion of 24 h resulted in Fiber E, for which only PDMS had been added, having the lowest soiling ratio. In contrast, Fibers L and G (produced by adding OA) had relatively high soiling ratios when immersed for a long time. The wear resistances of knitted fabrics were evaluated using an abrasion tester. Fabric made from pure PP fibers had holes after 20 cycles of abrasion, whereas fabrics formed from fibers to which PDMS and/or OA had been added did not have holes even after 100 cycles of abrasion, which represents a remarkable improvement in wear resistance.

Acid Treatment of Titania Pastes to Create Scattering Layers in Dye-Sensitized Solar Cells

In dye-sensitized solar cells (DSC) scattering layers are used to increase the path length of light incident on the TiO2film. This is typically achieved by the deposition of an additional TiO2layer on top of an existing transparent film and designed to trap light. In this work we show that a simple acid pretreatment can lead to the formation of a scattering “skin” on the surface of a single TiO2film performing a similar function to a scattering layer without any additional depositions. This is important in increasing manufacturing throughput for DSCs as further TiO2depositions require additional materials and heat treatment. The pretreatment leads to self-assembly of a scattering layer of TiO2which covers the surface on short-term immersion (<30 min) and penetrates the bulk layer upon longer immersion. The method has been shown to increase the efficiency of the device by 20%.

Effect of RE on Anti-Corrosion Mechanism of Arc Sprayed Zn-Al-Mg Coatings

In order to study the effect of RE on anti-corrosion mechanism, high Mg content Zn-Al-Mg and Zn-Al-Mg-RE (where RE is Rare Earth) alloy coatings were produced on low carbon steel substrates by using cored wires and arc spraying. The electrochemical impedance spectroscopy (EIS) was used to determine the anti-corrosion mechanism of the two coatings in 5% NaCl solution. The composition and structure of corrosion products on the coatings surface have been investigated after corrosion tests by X-ray diffractometer (XRD). The results show that, Zn-Al-Mg-RE coating has superior corrosion resistance compared to Zn-Al-Mg coating due to the formation of more compact and uniform corrosion products. The self-sealing effect of the Zn-Al-Mg-RE coatings, especially for longer immersion times is extremely good. The role of the RE elements appears to be associated with the self-sealing process and the refinement of the coating microstructure.

Evaluation of structural integrity and mechanical behavior of advanced FRP composites

PurposeThe purpose of this paper is to analyze microstructural integrity at the interface and consequent implicating effect on mechanical behavior of fiber‐reinforced polymer composites.Design/methodology/approachIn the light of Fourier transform infrared spectroscope (FTIR imaging) and temperature‐modulated differential scanning calorimeter, a sorption mechanism was established. Thermal spike and thermal shock treatment was carried out at 150 and 80°C, respectively. This suggested that fiber/matrix adhesion rests on the structure and properties of both the fiber and matrix in the region near the interface during the hygrothermal treatment.FindingsThe carbon surface was found to selectively absorb the tertiary amine catalyst and to modify the chemical state of the cured resin apparently through the effects of absorbed water. The higher values of glass transition temperature (Tg) resulted in longer immersion time and higher exposure temperature. Together, these techniques provide a comprehensive picture of chemical and physical changes at the interphase region. Thermal spike of hybrid composite at 150°C temperature might possibly improve the adhesion level at the interface. Whereas, in case of thermal shock treatment at 80°C the fall in inter‐laminar shear strength value at higher number of cycles. This degradation of the interface region has been monitored by scanning electron microscope analysis.Originality/valueThe reported data are based on experimental investigation.

Behavior of NiTi in the presence of oral bacteria: Corrosion by Streptococcus mutans

The aim of this study was to investigate the electrochemical behavior of nickel titanium (NiTi) orthodontic wires in a solution containing Streptococcus mutans oral bacteria. In this article, we explain our choice of bacterial species before describing the culture process in artificial saliva and the precautions needed to prevent contamination by other bacteria. The electrochemical behavior of the alloy (NiTi) was analyzed electrochemically in Ringer sterile artificial saliva and in artificial saliva enriched with a sterile broth and modified by addition of bacteria. The electrochemical procedures chosen for this study were: free corrosion potential, potentiodynamic curves and impedance spectroscopy. In this way, we were able to show that the free corrosion potential of the NiTi in the Ringer solution increases with time and then stabilizes, thus passivating the alloy. We also demonstrated that colonization of the metal surface by bacteria triggered a drop in the free corrosion potential. The electrochemical impedance findings revealed no significant difference in NiTi behavior between the two media. Finally, we observed a slight difference between the two corrosion currents in favor of the bacteria-enriched solution, in which the NiTi underwent greater corrosion. These findings demonstrate the impact of acidogenic bacteria on corrosion behavior of the NiTi wires investigated. However, further research is required, notably incorporating longer immersion times in the two media.

Initiation and formation of electroless nickel–boron coatings on mild steel: Effect of substrate roughness

The initial deposition and growth of electroless nickel–boron deposits on mild steel were studied: the films were prepared in an electroless plating bath using sodium borohydride as reducing agent. Samples were immersed in the plating solution for times from 5 s to 1 h and the morphological evolution of the deposit was followed by scanning electron microscopy (SEM) observation of the surface and prepared cross sections. Energy dispersive X-ray spectrometry (EDX) and glow discharge optical electro spectroscopy (GDOES) analyses were used to obtain information about the chemistry of the deposits and their results were correlated with the morphology of the coating. The initiation mechanism of electroless deposition on mild steel was identified. The effects of substrate roughness variation on the morphology and growth rate of the coatings were investigated by reproducing the experiment on samples with various surface preparation (grinding) states. We observed that the increase of substrate roughness favors the deposit initiation: the density of nickel nodules increases with increasing roughness of the substrate. Longer immersions in the bath lead to homogenization and densification of the coating and the nodules are clearly distinguishable.

Characterisation of interface formed at 650°C between AISI H13 steel and Al–12Si–1Cu aluminium melt

Quenched and tempered, nitrided and oxidised die casting pins were tested in order to evaluate their response to the corrosion imposed by the contact against a molten aluminium alloy. A static immersion apparatus was used to maintain the pin surfaces, and the aluminium alloy melt at 650°C from 5 up to 50 000 s. The pins were characterised by scanning electron microscopy using advanced electron dispersive X-ray spectroscopy capabilities that enable deeper characterisation of the soldering phenomenon occurring in steel/molten aluminium alloy interfaces. The achieved results indicate that nitrided and oxidised surfaces present non-wetting behaviour, whereas the quenched and tempered surface is easily wetted. Mechanical soldering occurs after short immersion times, while chemical soldering takes place for longer immersion periods. Chemically soldered material is composed of four layers. The two nearest layers from steel are the intermetallics Al5(Fe, Mn, Cr)2 and Al12(Fe, Mn, Cr)3Si2. The third layer has a chemical composition that resulted from the aluminium alloy enrichment with Fe, Cr and Mn. The outer layer corresponds to the solidified aluminium alloy. The growth equations for the four layers of the quenched and tempered samples were identified, and a formation mechanism for intermetallic phases is proposed.

Effects of concentration and propagule age on the efficacy of gibberellic acid for breaking dormancy in potato minitubers

SummaryThe effects of a post-harvest application of gibberellic acid (GA3) at various concentrations (0, 10, 25, 50, or 100 mg l–1) and for different periods of incubation (1, 2, or 3 h) on the breaking of dormancy and on sprouting in potato (Solanum tuberosum L., cv. Marfona) minitubers of two ages (freshly-harvested or 1 week after harvest) were investigated. Compared with untreated, control minitubers, GA3-treated minitubers showed a significantly shorter period of dormancy (46 d), especially when the minitubers were treated at all concentrations immediately after harvest (41 d). GA3 treatment had a greater effect on dormancy in freshly-harvested minitubers than in 1 week-old minitubers, probably because of the reduced uptake of GA3 solution after skin-set. At lower concentrations of GA3, the period of dormancy tended to decrease the longer the minitubers were immersed in the GA3 solution. In contrast, at higher concentrations of GA3, the duration of immersion only had an effect up to 2 h and any longer immersion was ineffective. The average number of sprouts was not affected by GA3 concentration, or by the time of incubation, but was significantly higher for freshly-harvested minitubers (1.4) than for 1 week-old minitubers (1.2). The lengths of the sprouts increased with an increase in GA3 concentration, especially in freshly-harvested minitubers. Consequently, immersing freshly-harvested potato minitubers in a low concentration of GA3 (up to 25 mg l–1) for up to 3 h effectively shortened the period of dormancy and led to the formation of sprouts of optimum length.