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A corrosion spreading throughout the 304 stainless steel tubing of a water system to supply various buildings was observed, and also leaks were detected in welding zones. The same place is also crossed by a gas distribution network, with a helium pipe 316 of stainless steel that required periodic repairs more or less every two years, due to the presence of leaks. The tests showed that both types of stainless steel have suffered localized corrosion induced by hypochlorite ion, in a mechanism of dry/wet, and that the welding procedure performed on the 304 stainless steel is unacceptable. Some immediate procedures were undertaken to keep systems running, but recommendations were given for a final resolution of the problems.

The metallization of acrylonitrile butadiene styrene (ABS) has been achieved using a new direct plating process that consisted of a previous treatment by polypyrrole (PPy) to transform the plastic conductor followed by direct copper electroplating. The deposition of PPy on ABS samples is reached chemically in a solution of pyrrole and iron(III) chloride as oxidant. The PPy synthesized is adherent to the plastic surfaces. Adherent copper layers with different thicknesses have been obtained on PPy/ABS at different electrolysis time. Energy dispersive X-ray spectroscopy (EDS) analysis revealed that copper is deposited on PPy/ABS surface. SEM analysis shows that increasing the electrolysis time increases the copper coating thickness.

Activated carbon xerogels with a cellular morphology were obtained from hydrothermally carbonized glucose-graphene oxide (GO) hybrids and tested as supercapacitor electrodes. The effect of the chemical activation (using KOH) on the nanometer-scale morphology, local structure, porous texture and surface chemistry of the resulting carbon materials was investigated and correlated with their electrochemical behaviour. The electrochemical performance of the activated xerogels was studied in a three-electrode cell using 1 M H2SO4 as the electrolyte. The results underlined the relevant role played by the xerogel nanomorphology; more specifically, xerogels with cellular structures exhibiting well-connected, continuous and very thin (∼5–15 nm) carbon walls (prepared with lower amounts of activating agent) favored ionic diffusion and electronic conduction compared to materials with broken, thicker walls (obtained from higher amounts of activating agent). The effect of nanomorphology and local structure was also made apparent when the xerogels were used as actual supercapacitor electrodes. Particularly, a symmetric capacitor assembled from a carbon xerogel with very thin walls and relatively high graphitic character delivered a much higher specific capacitance than that of a commercial activated carbon (223 vs 153 F g−1 at 100 mA g−1) as well as a significantly improved retention of capacitance at high current densities., This work was financed by QREN, ON2, FCT and FEDER (Project NORTE-07-0124- FEDER-000015 and NORTE-07-0162-FEDER-000050), and co-financed by FCT and FEDER through COMPETE 2020 (Project UID/EQU/50020/2013 - POCI-01-0145- FEDER-006984). Partial funding of this work by the Spanish MINECO and the European Regional Development Fund (projects MAT2015-69844-R and MAT2012- 34011) is also gratefully acknowledged.

Tinplate steel cans were used to store contact glue for shoes. A few months after its storage, the glue displayed a change in colour to a darker brown. The visual inspection of the interior of the cans showed the presence of corrosion of steel, which was evidenced by the typical colour of the iron oxides on the sheet. SEM/EDS and FTIR tests confirmed that the anomaly was due to the following factors: (a) a bad tin coating, small thickness and lack of homogeneity; (b) a degradation of glue, hydrolysis of chloroprene, which led to its acidification. Some recommendations are made to overcome similar situations within the same use of these packages looking at the specifications of tinplate.

Nickel electroplating of acrylonitrile butadiene styrene (ABS) plastic has been achieved successfully without any chromium or palladium pretreatment. Once the ABS is coated with polypyrrole (PPy), the sample may be electroplated. The process is fast, economic and involves three stages. Firstly, chemical deposition of PPy on ABS, secondly, copper deposition and finally nickel electroplating. A homogenous and adherent PPy has been synthesized chemically on ABS plate by using pyrrole as monomer and iron (III) chloride as oxidant. Copper and nickel were deposited galvanostatically from industrial plating baths. The metallic coatings were homogeneous and the adherence was estimated at 100%. The thickness of copper and nickel depend on the electrolysis time. As the current density increases, the Cu and Ni thickness raises. This result was confirmed from SEM characterization and RX map. The Ni coating is characterized by a globular structure with globules of different sizes. Energy dispersive X-ray spectroscopy (EDS) analysis shows the presence of Ni with some amount of carbon and oxygen due to the nickel oxides and contaminant from the bath solution.

This work relates a study on a medieval coin found during archaeological works carried out at the site of Senhora do Castelo in Urros (Torre de Moncorvo, Portugal). The artefact has been identified as a coin of D. Afonso IX of Leon (1155–1188). The substratum showed composition typical of bullion, Cu-Ag (30–33%) with minor elements (1% Pb + 0.2% Sn + 0.4% Zn). The corrosion products developed on the coin during the archaeological burial was studied by means of optical microscopy (OM), scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS), energy dispersive X-ray fluorescence (EDXRF), and X-ray diffraction (XRD). The results show the presence of cuprite, atacamite, chalcocite, native silver, silver oxide and silver sulphide on the outer layers of the coin, which allows deducing the importance of the environment in the corrosion phenomena.

The electrochemical behaviour of dimethylamine borane and borohydride on platinum electrodes was investigated by cyclic voltammetry and polarization curves in discharges processes. Several overlapping peaks appear in the domain of hydrogen oxidation, i.e., in the potential range of −1.25 V to −0.50 V versus Ag/AgCl, mainly with the borohydride. This behaviour is associated with the hydrolysis of BH 4 − or (CH 3 ) 2 NHBH 3 . As a consequence of secondary reactions the borohydride and dimethylamine borane oxidation in 3 M NaOH solution shows, respectively, a four- to six-electron process and a four- to five-electron process in direct fuel cells. The direct oxidation of the borohydride exhibits a peak at about −0.07 V versus Ag/AgCl, while the dimethylamine borane peak is at about −0.03 V versus Ag/AgCl. For the 0.04 M concentration the borohydride displays a power density of 31 W m −2 which is 16% higher than that of the dimethylamine borane.

Cerium oxide/multiwalled carbon nanotube composites with different oxide loadings (5–60 wt. %) were prepared by sol-gel deposition of the oxide onto the carbon support. The morphology, texture and surface properties of the prepared materials were studied and correlated with their electrochemical behavior. The different charge storage mechanisms occurring on the surface of the composites were successfully identified by a newly developed electrochemical method, namely the combination of sweep wave voltammetry with deconvolution analysis in 1 M H 2 SO 4 . The deposition of moderate oxide loadings (up to 10 wt. %) leads to small and well distributed oxide particles on the nanotubes surface. Therefore, the appearance of defects on the oxide structure is favored, promoting both electronic conduction and faradaic activity. Curiously, cerium oxide loadings above 10 wt. % induce a higher dispersion of the carbon support. This convenient synergism enhances the electroactive area of the composites by increasing molecular diffusion.

The electrochemical behaviour of sodium borohydride on a platinum electrode in the absence and presence of thiourea (TU) was investigated by cyclic voltammetry. In the absence of thiourea, several overlapping peaks associated with the hydrolysis of BH4− appear in the domain of hydrogen oxidation, i.e., in the potential range of −1.25 to −0.50 V versus Ag/AgCl. As a consequence of secondary reactions, the borohydride oxidation in 3 M NaOH solution shows a four to six-electron process, according to its concentration, in direct fuel cells. A conveyable TU/NaBH4 concentration ratio of 0.6 inhibits the delivery of hydrogen simultaneously with catalytic hydrolysis of BH4−. Thus, the coulombic efficiency in direct fuel cell discharge was increased showing an about eight-electron process for the oxidation of BH4−.

The recovery of tungsten from alkaline leach solutions has been studied examining the effect of temperature, pH, Ca/WO3 molar ratio and nature of the precipitated calcium tungstate. The precipitation kinetics of calcium tungstate, upon the addition of aqueous sodium tungstate to calcium solutions, was followed by potentiometric measurements using a calcium ion-selective electrode. Two models, a crystal growth model and a second-order reaction opposed by zero-order reaction, have been used to test the experimental data. Both models show that the apparent activation energy of CaWO4 precipitation falls in the range 58 to 67 kJ mol− 1. The kinetic data shows that the maximum recovery of precipitated calcium tungstate occurs at pH ≥ 8.5 with a 10% excess of CaCl2 at 50 °C over a period of 20 min using sodium tungstate solutions of 100 g L− 1 and 150 g L− 1 WO3.

The electrochemical synthesis of polypyrrole (PPy) on copper and brass has been successfully achieved in sodium saccharinate and pyrrole aqueous medium. The synthesized coating under several electrochemical techniques such as cyclic voltammetry, galvanostatic and potentiostatic is homogeneous and adherent. PPy has been characterized by SEM, XPS, IR and Raman spectroscopy and its quality has been confirmed. The doping level obtained from N 1s XPS signal of the oxidized PPy depends on the electrochemical technique used to produce the film. The corrosion performance of PPy/copper and PPy/brass has been evaluated in 3% NaCl and 0.1 M HCl using linear polarization and electrochemical impedance spectroscopy. The results show that PPy coating electrodeposited from sodium saccharinate exhibits significant corrosion protection properties.

The electrosynthesis of polypyrrole (PPy) has been achieved on aluminium in aqueous medium of malic acid by means of cyclic voltammetry, potentiostatic and galvanostatic techniques. Scanning electron microscopy (SEM) and X-ray microanalysis by dispersion energy spectroscopy (EDS) applying on surfaces show that the PPy coating is developed from the metal surface through the cracks of the initial Al 2 O 3 layer. Moreover, the results reveal that the homogeneity of the film achieved increases with the time of electropolymerization. A mechanism involving the participation of the supporting electrolyte and the pyrrole (Py) in distinct active sites was proposed based on the linear sweep voltammetry. It is observed for all the applied electrochemical techniques that the pyrrole concentration has to be higher than 0.1 M to allow the polypyrrole electrodeposition in acid medium. Scanning electron microscopy, secondary electrons (SE) and backscattering electrons (BE), shows that the PPy coating obtained in galvanostatic and potentiostatic modes starts with small islands at weak applied potentials or current densities. The corrosion results in 3% NaCl medium show that the PPy coating decreases the corrosion behaviour of the aluminium. The bilayer Al 2 O 3 /PPy shows a capacitor with future applications.

The electrosynthesis of polypyrrole (PPy) has been achieved on aluminium in aqueous medium of tartaric acid by means of cyclic voltammetry, potentiostatic and galvanostatic techniques. Scanning electron microscopy (SEM) and X-ray microanalysis by energy spectroscopy dispersion (EDS) applying on surfaces show that the PPy coating is developed from the metal surface through the cracks of the initial Al2O3 layer. A mechanism involving the participation of the supporting electrolyte and the pyrrole (Py) in distinct active sites was proposed based on the linear sweep voltammetry. It is observed for all applied electrochemical techniques that the pyrrole concentration has to be higher than 0.1 M to allow the polypyrrole electrodeposition in acid medium. Scanning electron microscopy, secondary electrons (SE) and backscattering electrons (BE), shows that the PPy coating obtained in galvanostatic and potentiostatic modes starts with small islands at weak applied potentials or current densities. Moreover, EDS reveals a good homogeneity and compactness of the film achieved in galvanostatic method. The corrosion results in 3% NaCl medium show that the PPy coating decreases the corrosion behaviour of the aluminium. The bilayer Al2O3/PPy shows a capacitor with future applications.

A single-step electropolymerization of pyrrole on zinc-coated steel electrodes in aqueous medium was investigated under several techniques (potentiodynamic, galvanostatic and potentiostatic modes) by using carboxylate salts, such as the citrate, the succinate, the oxalate, the malate and the tartrate. Adherent and homogeneous PPy coatings were obtained only with tartrate counter-ions. The corrosion behaviour of zinc-coated steel electrodes electrochemical modified by PPy films were estimated by open circuit potential and DC polarization in NaCl, HCl and H2SO4 aggressive solutions. The obtained results show that the PPy coatings increase the corrosion potential and reduce the corrosion current. The salt spray test results show that the PPy coating prepared under ultrasonic waves is more resistant than those obtained in normal conditions.

The electrosynthesis of polypyrrole (PPy) on copper and brass (Cu–Zn alloy) electrodes was performed by anodic oxidation of pyrrole in a sodium tartrate (C4H4Na2O6 0.2 M) aqueous solution. The tartrate counter-ions slow the dissolution of the working electrode by leading to formation of a passivation layer on its surface, and pyrrole electropolymerization takes place. Strongly adherent and homogeneous polypyrrole films were electrodeposited on Cu and Cu–Zn alloy electrodes using different electrochemical techniques, such as potentiodynamic, galvanostatic and potentiostatic modes. The current densities of electropolymerization on brass are generally greater than those observed on copper. The corrosion behaviour of copper-coated electrodes, electrochemically modified by PPy films, was estimated by DC polarization and weight loss at different current densities in 0.1 M HCl solution. The synthesized polypyrrole films were characterised by several microscopic and spectroscopic techniques such as scanning electron microscopy, X-ray photo electron spectroscopy, Fourier transform infrared and Raman analysis. Galvanostatically deposited PPy films are shown to be an alternative to common black-nickel or black-chromium as a decorative top-coating.

The kinetics of the leaching reaction of synthetic scheelite with hydrochloric acid was studied to determine the effect of pH and temperature in the formation of tungstic acid. Conversion data obtained from leaching in a temperature range of 28–100 °C and pH between 1.5 and 3.0 are interpreted in terms of the predominating tungsten species present in the leaching liquors. The results show that it is possible to digest the synthetic scheelite in the acidic hydrochloric medium without the formation of tungstic acid by monitoring and controlling the pH, and controlling the temperature in the domain of metatungstates. In this case, the experimental results match with the shrinking core model, and show that the solids leaching is kinetically under both chemical and mass transfer control.

Hierarchical carbons with different boron contents (from 0.42 to 2.37 wt.%) were prepared by combination of soft-templating and hydrothermal approaches. This newly developed strategy enables adequate control of the chemical state of the boron functionalities in carbon materials since the self-generated pressures favour B–C bond formation. The total content of oxygen increases simultaneously with the boron content, and its speciation is also influenced by the boron chemical state distribution: the presence of C–B–C (BC 3 and BC 2 O) species induces the oxidation of phenols to carbonyls. The electrochemical performance of the prepared carbons was tested in a three-electrode cell configuration (1 M H 2 SO 4 ) showing good specific capacitances per BET specific surface area (20–36 μF/cm 2 ). The presence of boron on the carbon backbone improves both the charge propagation and the pseudocapacitive properties. Nevertheless, the electrochemical properties are only enhanced up to some level of boron doping (around 1.8 wt.%). A two-electrode supercapacitor built with a carbon prepared by a mild hydrothermal synthesis (50 °C during 28 h) delivered energy densities similar to those of commercial activated carbons. This could lead to high volumetric capacitance, since the boron doped carbons present much higher density.

Electropolymerization of pyrrole on zinc–lead–silver (Zn–Pb–Ag) alloys was carried out in acetonitrile, nitrobenzene and propylene carbonate (PC) organic media in the presence of para -toluene sulfonate counter ions. Adherent and homogeneous PPy films have been obtained on zinc alloy electrodes (65% Zn, 10% Pb and 25% Ag) prealably treated with aqueous sodium sulfide solution. Among the electrochemical techniques used in these experiments, the galvanostatic mode was proved to be better adapted to perform the electrosynthesis of polypyrrole using low applied current densities. The PPy coatings have been characterized by different microscopic and spectroscopic techniques. Scanning electron microscopy (SEM) showed that PC (DN=15.1) is the most suitable solvent for elaborating high-quality and thick PPy films. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) analysis proved that the obtained coatings have the same structure properties as those electrodeposited on noble Pt plates.

The electrodeposition of polypyrrole on zinc electrodes has been performed by anodic oxidation of pyrrole in acetonitrile, nitrobenzene and propylene carbonate media in the presence of para-toluene sulfonate counter-ions. When the zinc electrode has preferably undergone a chemical treatment by aqueous sodium sulfide solution, homogeneous and adherent PPy films are obtained. While, no PPy film grows (in the case of C6H5NO2 and PC) or a non-homogeneous and poorly adherent PPy–zinc oxide composite forms (in the case of CH3CN) when the zinc surface is simply polished. Among the electrochemical techniques used in these experiments, the galvanostatic mode was proved to be better adapted to perform the electropolymerization of pyrrole on the pretreated zinc electrodes using low applied current densities. The polypyrrole films synthesized by this technique has been characterized by several microscopic and spectroscopic techniques. In particular, SEM, XPS, FT-IR and Raman analyses showed that the obtained coatings have the same structure and morphological properties as those electrodeposited on Pt electrodes.

Results are presented on the electrical characteristics of power diodes soldered using new lead-free techniques based on Cu–Sn–Cu joints. Special emphasis is put on the role of the thickness of the Cu films electrodeposited on the electrical performances of the power diodes joined and to study the electrical stability of the joints formed, under extreme aggressive conditions.

The electrodeposition of polypyrrole (PPy) on aluminium electrodes has been achieved in phosphoric acid medium by using potentiodynamic, potentiostatic and galvanostatic techniques. The corrosion behavior of polypyrrole on aluminium in sodium chloride medium has been investigated by open circuit potential and electrochemical impedance spectroscopy. A mechanism to explain the beneficial effect of PPy-doping dihydrogenophosphate ion in the passivation of aluminium is proposed. A electrodeposição do polipirrole (PPy) sobre alumínio em soluções de ácido fosfórico foi obtida através de técnicas potenciodinâmicas, potenciostáticas e galvanostáticas. O comportamento do alumínio revestido com polipirrole em meio de cloreto de sódio foi investigado através do potencial de circuito aberto e espectroscopia de impedância electroquímica. É proposto um mecanismo para explicar o efeito benéfico do íon dihidrogenofosfato na passivação do alumínio.

The reaction kinetics for the leaching of synthetic scheelite with nitric acid was studied to establish the effect of pH and temperature in the formation of tungstic acid. The yield of the leaching reaction in the temperature range of 30-90 °C and at pH between 1.5 and 3.0 is analyzed in terms of prevailing tungsten species present in the leaches. The results show that tungstic acid can be avoided during the digestion of synthetic scheelite in the acidic medium by monitoring the pH and controlling the temperature in the domain of metatungstates. In this case, the experimental results match those of the shrinking-core model and show that the solids leaching is under both chemical and mass-transfer control.