Highly robust stainless steel tips as microelectrospray emitters

Tapered stainless steel spray tips for sheathless microelectrospray ionization (microESI) have been developed. The fabrication procedure for the tapered stainless steel tips was optimized using an electropolishing technique followed by removal of the burr. Using the tip as the microESI emitter, a stable ESI spray was obtained at a flow rate of 20 nL/min. The sensitivity of the microESI system was almost two orders greater than that of the conventional ion spray system. The tip was highly stable, and was successfully used for over 1000 h. Moreover, these stainless steel tips were suitable for use with sheathless capillary electrophoresis/mass spectrometry (CE/MS) and capillary liquid chromatography/mass spectrometry (LC/MS) for routine analysis in proteomic and pharmaceutical applications.     

Miniaturized reference electrodes with stainless steel internal reference elements

Stable reference electrodes have previously been obtained by immersion of a stainless steel internal reference element (SSIRE) in a solution of steady pH, e.g., a stainless steel wire maintained in 2 mol/l HCl. Here, we report the miniaturization of this regular size reference half-cell by embedding thermally activated SSIREs in a copolymer matrix of a fixed and constant pH value. The resulting electrode is based on a polymer volume of 1-5 μl, while its contact area at the polymer/analyte solution interface is 0.4 mm². Photopolymerized acrylic type hydrogel is used as the copolymer which contains a quaternary ammonium salt as the supporting electrolyte. These miniaturized reference electrodes show potential stability over the pH range of 1-13, maintain a constant potential value over the time, and are suitable for potentiometric and voltammetric measurements in both aqueous and organic media. Furthermore, they do not exhibit leakage problems. Hence, they do not contaminate the analytical sample, even when the reference electrodes (REs) are used in very small volumes and over extended period.     

Corrosion inhibition of 302 stainless steel with schiff base compounds

The effects of 2,2′-[bis-N(4-cholorobenzaldimin)]-1,1′-dithio (BCBD) and bis-(2-aminophenyl) disulphide (BAPD) on the corrosion behavior of 302 stainless steel in 0.5 M sulfuric acid solution as corrosive medium were investigated using weight loss and potentiostatic polarization techniques. Some corrosion parameters such as anodic and cathodic Tafel slopes, corrosion potential, corrosion current density, surface coverage degrees and inhibition efficiencies were calculated. The polarization measurements indicated that the inhibitors were of mixed type which inhibited corrosion by parallel adsorption on the surface of stainless steel due to the presence of more than one active centre in the inhibitor molecule. The adsorption followed Langmuir adsorption isotherm. The activation energy and thermodynamic parameters were calculated at different temperatures. Results showed that BCBD had a higher inhibition efficiency compared with BAPD.     

AFM and FTIR studies of organic cation adsorption on carbon steel coupled with stainless steel

The electrochemical behavior of the anode of the galvanic couple and the adsorption behavior of the cationic inhibitor on it have been investigated by using electrochemical methods, atomic force microscopy (AFM) and infrared spectroscopy (FTIR) technology. A galvanic electrode was prepared by coupling N80 carbon steel (CS) and S31803 stainless steel. All experiments were performed in NaCl solution in the presence or absence of an inhibitor. The results show that, in aqueous NaCl solution, CS carries negative excess charge, for the couple, positive charge is carried on the CS side (anode). The adsorption behavior of the cationic inhibitor on CS is significantly affected by the excess charge carried on it. Owing to the charge interaction between electrodes and the cationic inhibitor, the inhibitor has a greater tendency to adsorb on the single CS and less tendency to adsorb on the CS of the couple. Because of this, the adsorption film on the anode (CS side) of the couple is thin and defective. The failure of inhibiting galvanic corrosion attributes to the defective protective layer formed on the anodic area. Copyright © 2006 John Wiley & Sons, Ltd.     

Potentiometric titration of hydrogen peroxide with an electropolished stainless steel electrode

The preparation and use of a stainless steel indicator electrode in the accurate potentiometric titration of aqueous hydrogen peroxide are described. The results agree excellently with those obtained by a standard colorimetric weight-titration procedure. The nature of the titration curves, potential changes and the factors affecting them are discussed. Rapid potentiometric titrations directly to the equivalence-point potential are possible, owing to the nature of the titration curve.     

Determination of stainless steel constituents in plastics

Summary Instrumental neutron activation analysis (INAA), atomic absorption spectrometry (AAS), and X-ray fluorescence analysis (XRF) were tested for the determination of the abrasion effect in plastics processing equipment. As optimal solution measurement of Fe by XRF in cylindrical samples was found.     

Breakdown potential modelling of austenitic stainless steel

The breakdown potential is a crucial factor in the study of pitting corrosion resistance of stainless steel. This work aims to demonstrate the advantage of different chemometric techniques to estimate the breakdown potential of austenitic stainless steel. In order to predict pitting corrosion behaviour of stainless steel, a total of 60 samples of this alloy were subjected to electrochemical tests varying chloride ion concentration, pH and temperature. The experimental values of the breakdown potential, in addition to the tested environmental factors, were used to construct the predictive models based on support vector machines and artificial neural networks. A multiple‐comparison study based on statistic tests was applied to determine the optimal configuration for each technique. According to the results, support vector machines became a suitable and reliable technique to be applied in the modelling of the breakdown potential of austenitic stainless steels. This technique outperformed the models based on artificial neural networks and provided a useful tool to compare the pitting corrosion resistance of stainless steel in different environmental conditions without recourse to polarization tests. Therefore, this model presented a relevant meaning in science and engineering applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Antibacterial polyelectrolyte micelles for coating stainless steel

In this study, we report on the original synthesis and characterization of novel antimicrobial coatings for stainless steel by alternating the deposition of aqueous solutions of positively charged polyelectrolyte micelles doped with silver-based nanoparticles with a polyanion. The micelles are formed by electrostatic interaction between two oppositely charged polymers: a polycation bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) and a polyanion (poly(styrene sulfonate), PSS) without using any block copolymer. DOPA units are exploited for their well-known ability to anchor to stainless steel and to form and stabilize biocidal silver nanoparticles (Ag(0)). The chlorine counteranion of the polycation forms and stabilizes biocidal silver chloride nanoparticles (AgCl). We demonstrate that two layers of micelles (alternated by PSS) doped with silver particles are enough to impart to the surface strong antibacterial activity against gram-negative E. coli. Moreover, micelles that are reservoirs of biocidal Ag(+) can be easily reactivated after depletion. This novel water-based approach is convenient, simple, and attractive for industrial applications.     

Micro-electrospray mass spectrometry: Ultra-high-sensitivity analysis of peptides and proteins

A “micro-electrospray” ionization source has been developed that markedly increases the sensitivity of the conventional electrospray source. This was achieved by optimization of the source to accommodate nanoliter flow rates from 300 to 800-nL/min spraying directly from a capillary needle that, for the analysis of peptides, contained C18 liquid chromatography packing as an integrated concentration-desalting device. Thus, a total of 1 fmol of methionine enkephalin was desorbed from the capillary column spray needle, loaded as a 10-μL injection of 100-amol/μL solution. The mass spectrum showed the [M + H]⁺ ion at m/z 574.2 with a signal-to-noise ratio of better than 5:1 from a chromatographic peak with a width of about 12 s. A narrow range (15-u) tandem mass spectrum was obtained for methionine enkephalin from the injection of 500 amol, and a full-scan tandem-mass spectrum was obtained from 50 fmol. For proteins, the average mass measurement accuracy was approximately 100–200 ppm for the injection of 2.5 fmol of apomyoglobin and 20–40 ppm for 200 fmol. Carbonic anhydrase B and bovine serum albumin showed similar mass measurement accuracies.     

Protective coatings for stainless steel for SOFC applications

In this paper, a coating procedure based on spin coating of metal oxide polymer precursors on stainless steel, which decreases the oxide scale growth rate, is evaluated. The yttrium and cobalt solutions were used as polymer precursors, while a ferritic stainless steel Crofer 22 APU was used for the deposition of protective coatings. The thickness of deposited protective film was about ~500 nm. The effectiveness of protective layer was evaluated by cyclic thermogravimetry, oxide scale electrical conductivity, and X-ray diffractometry. The results show that steel coated with yttrium polymer precursor has better properties than uncoated or cobalt-coated sample.     

Hydrolysis and grafting of dimethylalkoxysilanes onto stainless steel

The grafting of trialkoxysilane molecules should also give rise to the formation of a siloxane network at the substrate's surface when trialkoxysilanes are used. Other candidates that might be able to act as adhesion promoters at metallic surfaces are dimethylalkoxysilanes. The advantage of dimethylalkoxysilanes is that only one silanol group is produced during the hydrolysis step, leading to the formation of a grafted monolayer onto the steel. Moreover, the chemical grafting of stainless steel, which exhibits a low surface reactivity, is of great interest for industrial applications such as adhesive bonding or coatings. The objective of this work was to chemically graft dimethylalkoxysilanes onto AISI 316L stainless steel and to analyze the grafted layer by X‐ray photoelectron spectroscopy (XPS). Investigation of the hydrolysis of these molecules in aqueous solutions was also performed by proton nuclear magnetic resonance spectroscopy (¹H NMR). The grafting of 3‐(ethoxydimethylsilyl)propylamine (APDES) and 3‐glycidoxypropyldimethylethoxysilane (GPDES) was achieved onto stainless steel after a controlled hydrolysis reaction. A pH inferior or equal to 5 was necessary to obtain a sufficient hydrolysis of silanes. XPS results have evidenced the grafting of the silanes onto stainless steel. The signal of the Si 2p peak clearly showed the formation of a covalent bond between APDES and the stainless steel surface through the O atoms giving rise to a uniform layer of adsorbed molecules. Moreover, this grafted layer is strongly stable as no removal of the alkoxysilane was observed after immersion in hot water which is very critical for these molecules. Copyright © 2015 John Wiley & Sons, Ltd.     

XPS study of mechanically polished stainless steel surfaces

The surface of a commercial sheet of AISI type 304 stainless steel has been examined by XPS technique in order to determine the effects of its composition of different heat treatments and polishing procedures. Sheet specimens have been solution annealed or sensitised and mechanically polished in water with different SiC papers. The surface respects to be enriched in chromium, to a greater extent in the solution annealed condition, with little influence of polishing conditions. The passive film appears to consist of Fe and Cr oxides and hydroxides, while no Ni has been detected. Chromium appears always in the 3+ oxidation level, while different oxidation levels are present for iron.     

Sol-gel coatings for chemical protection of stainless steel

Sol-gel thin coatings of ZrO₂, SiO₂, 70SiO₂-30TiO₂ and 88SiO₂-12Al₂O₃ compositions (mole %) have been prepared from sonocatalyzed sols and deposited by dip-coating technique on 316L stainless steel foils. The influence of the coatings on the chemical corrosion of the substrate has been measured through potentiodynamic polarization curves in aqueous 15% H₂SO₄ solution between 25 and 50°C. The values of the corrosion potential, polarization resistance and corrosion rate have been determined. Analysis of the data combined with scanning electron microscopy studies indicate that the films act as a geometric blocking against exposure to the corrosive media and increase the lifetime of the substrate up to a factor 8.5.     

Investigation of oxide films on ferritic stainless steel

Summary While annealing cold-rolled strip of ferritic stainless steel in protective atmosphere oxide films may form on the surface. These parts of strip are defective material because of their deteriorated workability and appearance. For detailed investigation of the structure of the oxide layers concerning chemical composition and thickness, they were analysed by SNMS, SEM, and chemical methods.The oxide layers which look yellowish, brown, blue or grey (annealing colours) have a max. thickness of 0.4 m. They consist of oxides of Cr, Mn, Si and Ti. Thickness, chemical composition, colour and the sequence of different oxides in the layer depend on annealing time, annealing temperature and the oxidation potential of the protective atmosphere.     

Hydroxyapatite coating on stainless steel pre-coated with bovine serum albumin at ambient conditions

A biomimetic process for coating of nanosized hydroxyapatite on stainless steel, which capitalises the dual nature of the protein bovine serum albumin in both metal binding and a strong affinity for calcium ions, has been developed. The novelty of the process lies in pre-conditioning the metallic surface using the above protein prior to its mineralization with hydroxyapatite at ambient conditions. The microporous morphology of these coatings may provide favourable solubility and resorbability as desired by many orthopaedic and orthodontic applications.     

Vacuum-assisted thermal bonding of plastic capillary electrophoresis microchip imprinted with stainless steel template

An improved fabrication of poly(methyl methacrylate) (PMMA)-based capillary electrophoresis microchips has been demonstrated. The microchannel structures on PMMA substrates were generated by one-step hot embossing procedure using a stainless steel template. Hundreds of patterned PMMA substrates have been successfully obtained using the single metal template. Sequent microchannel enclosure with high yield up to 90% was accomplished by a vacuum-assisted thermal bonding method. The results of profilometric scanning of separated substrates showed the dimensions of the channels were well preserved during the bonding process. Finally, analytical functionalities of these PMMA microchips were demonstrated by performing fast electrophoretic separations and high sensitive end-column amperometric detections of dopamine and catechol. The entire fabrication methodology may also be useful for preparation of other thermoplastic microfluidic systems.     

Comparison of antibacterial ability of copper and stainless steel

In this paper, the electro-analysis and spectrophotometric analysis methods were used to study the antibacterial ability of copper and stainless steel materials. When Escherichia coli (E. coli) and photo-bacteria were used as samples, the antibacterial effect of stainless steel was very weak, while the percentage of bacteria dying from exposure to metallic copper for 30 min was over 90%. The antibacterial ability of copper has a potential application in the field of disinfection, food packaging and piping of drinking water. Translated form Huaxue Tongbao, 2006, 69(10): 772–776 (in Chinese)     

Sol-gel alumina coatings on stainless steel for wear protection

The aluminium oxide films on austenitic steel are prepared from sols of re-dispersed boehmite nano powders in water. After dip-coating of the sol, a heat treatment including drying, calcination and annealing in vacuum at temperatures up to 1100°C is performed to obtain crack-free coatings of a thickness up to 6 μm. XRD measurements detect α- and γ-alumina, a TiO_x-phase at the metal/coating interface and a gradient of phase formation in the coating. The strong adhesion on the substrates is due to the layered assembly and gradient composition of the coating caused by an inter-diffusion of metal cations and oxygen in the metal/oxide interface during heat treatment. Residual stress measurements by X-rays result in compressive stresses of 2–4 GPa in the alumina coatings. The pin-on-disc test shows a remarkable improvement of wear resistance obtained by sol-gel coatings. The α-alumina content and the compressive stress of the coatings correlate with wear resistance of the coatings.