Electrical behaviour, characteristics and properties of anodic aluminium oxide films coloured by nickel electrodeposition

Porous anodic films on 1050 aluminium substrate were coloured by AC electrodeposition of nickel. Several experiments were performed at different deposition voltages and nickel concentrations in the electrolyte in order to correlate the applied electrical power to the electrical behaviour, as well as the characteristics and properties of the coatings. The content of nickel inside the coatings reached 1.67 g/m2, depending on the experimental conditions. According to the applied AC voltage in comparison with the threshold voltage Ut, the coating either acted only as a capacitor when U\Ut and, when U[Ut, the behaviour during the anodic and cathodic parts of the power sine wave was different. In particular, due to the semi-conducting characteristics of the barrier layer, additional oxidation of the aluminium substrate occurred during the anodic part of the electrical signal, whilst metal deposition (and solvent reduction) occurred during the cathodic part; these mechanisms correspond to the blocked and pass directions of the barrier layer/electrolyte junction, respectively

Metal alloys, matrix inclusions and manufacturing techniques of Moinhos de Golas collection (North Portugal): a study by micro-EDXRF, SEM–EDS, optical microscopy and X-ray radiography

"Article:820"A collection of 35 metallic artefacts comprising various typologies, some of which can be attributed to the Bronze Age and others to later periods, were studied to provide detailed information on elemental composition, manufacturing techniques and preservation state. Elemental analysis by micro-EDXRF and SEM–EDS was performed to investigate the use of different alloys and to study the presence of microstructural heterogeneities, as inclusions. X-ray radiography, optical microscopy and SEM–EDS were used to investigate manufacturing techniques and degradation features. Results showed that most of the artefacts were produced in a binary bronze alloy (Cu–Sn) with 10–15 wt% Sn and a low concentration of impurities. Other artefacts were produced in copper or in brass, the latest with varying contents of Zn, Sn and Pb. A variety of inclusions in the metal matrices were also found, some related to specific types of alloys, as (Cu–Ni)S2 in coppers, or ZnS in brasses. Microstructural observations revealed that the majority of the artefacts were subjected to cycles of thermomechanical processing after casting, being evident that among some artefacts different parts were subjected to distinct treatments. The radiographic images revealed structural heterogeneities related to local corrosion processes and fissures that seem to have developed in wear-tension zones, as in the handle of some daggers. Radiographic images were also useful to detect the use of different materials in one particular brass artefact, revealing the presence of a possible Cu–Sn solder.This work was funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT— Fundação para a Ciência e a Tecnologia under the project UID/CTM/ 50025/2013 to CENIMAT/I3N. C2 TN/IST authors gratefully acknowledge the FCT support through the UID/Multi/04349/2013 project. EF acknowledges FCT for the grant SFRH/BPD/97360/2013. JF acknowledge FCT for the grant SFRH/BD/65143/2009. Part of this project has been done in the framework of the FCT project ENARDAS (PTDC/HISARQ/112983/2009).info:eu-repo/semantics/publishedVersio

FIB-FESEM and EMPA results on Antoninianus silver coins for manufacturing and corrosion processes

[EN] A set of ancient Antoninianus silver coins, dating back between 249 and 274¿A.D. and minted in Rome, Galliae, Orient and Ticinum, have been characterized. We use, for the first time, a combination of nano-invasive (focused ion beam-field emission scanning electron microscopy-X-ray microanalysis (FIB-FESEM-EDX), voltammetry of microparticles (VIMP)) and destructive techniques (scanning electron microscopy (SEM-EDX) and electron microprobe analysis (EMPA)) along with non-invasive, i.e., micro-Raman spectroscopy. The results revealed that, contrary to the extended belief, a complex Ag-Cu-Pb-Sn alloy was used. The use of alloys was common in the flourishing years of the Roman Empire. In the prosperous periods, Romans produced Ag-Cu alloys with relatively high silver content for the manufacture of both the external layers and inner nucleus of coins. This study also revealed that, although surface silvering processes were applied in different periods of crisis under the reign of Antoninii, even during crisis, Romans produced Antoninianus of high quality. Moreover, a first attempt to improve the silvering procedure using Hg-Ag amalgam has been identified.Financial support was provided by Sapienza University of Rome (Ateneo funding, 2014 15) and Spanish projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P, which are supported with Ministerio de Economía, Industria y Competitividad (MINECO) and Fondo Europeo de Desarrollo Regional (ERDF) funds, as well as project CTQ2017-85317-C2-1-P supported with funds from, MINECO, ERDF and Agencia Estatal de Investigación (AEI). PhD grants of the Department of Earth Sciences, Sapienza University of Rome, are gratefully acknowledgedDomenech Carbo, MT.; Di Turo, F.; Montoya, N.; Catalli, F.; Doménech Carbó, A.; De Vito, C. (2018). 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The use of triaiylmethane dyes on aluminium

Coatings have been formed on the surface of unanodised aluminium electrolytically treated in an aqueous solution of tin sulphate and a triarylmethane dye. The coatings produced had a good decorative appearance, good adhesion and were 3-5 μm thick. The coloured films had excellent light fastness but poor resistance to corrosion resistance. The dyes showing the most promise for this appication were Cl Acid Blue 9 and Cl Acid Green 5. These dyes interfered in the current flow, in so doing modifying the surface topography and the semiconductive properties of the superficial aluminium oxide film formed during the colouring treatment. The dye fragmentation, cyclisation and dimerisation products derived during the electrolytic treatment resulted in the formation of organotin compounds

Investigation of the relationship between the reflectance and the deposited nickel and tin amount on the aluminium anodic oxide film

Two distinct methods were used, energy dispersive X-ray fluorescence and specular reflectance measurement, in order to analyze the amount of the nickel and tin layers on anodic aluminium surfaces. These metals were electroplated at the bottom of the pores of anodized aluminium, during electrolytic colouring in solutions containing nickel borate and boric acid, tin sulphate and sulphuric acid, respectively. An exponential relation was derived giving the absorbance of each sample as a function of the surface density of the deposited metal. Various organic additives that improve the efficiency of the electrolytic procedure were used as well as AC or DC current which affects the situation of the anodic film; their influence on the calculated parameters was also investigated. © 1998 Elsevier Science S.A. All rights reserved

Effect of alloy types on the electrolytic coloring process of aluminum

The AC electrolytic coloring process at 15 Vrms in acidic tin sulfate solutions for specimens of AA 5083, AA 6111 unheat- and heat-treated was investigated in comparison with pure aluminum. For this purpose, electrochemical techniques, SEM/EDS and XRF were used. The specimens were anodized in sulfuric acid baths under different conditions, prior to electrolytic coloring. The alloy type affects the rate of tin deposition but certain qualitative characteristics and basic aspects of electrolytic coloring mechanisms are similar for alloys and pure aluminum. The temper of AA 6111 does not affect the electrolytic coloring process, although it influences the anodizing process. Under standard electrolytic coloring conditions, the current efficiency for tin deposition is low for all examined materials. However, pure aluminum has a much higher tin deposition efficiency than the alloys. A reduced amount of deposited metal with prolonged electrolytic coloring is observed for AA 6111, indicating deterioration of oxide structure during coloring process. For AA 5083, the increase of conductance of the oxide film results in an increase of the rms current and faradaic cathodic charge consumed during the electrolytic coloring process in comparison with the pure aluminum; this results in an increase of hydrogen evolution with no improvement in tin deposition efficiency. The anodizing voltage affects the electrolytic coloring process to a lesser degree for alloys than for pure aluminum, indicating the role of the morphology of the oxide film. The increases of anodizing temperature and porous layer thickness have marginal effect on electrolytic coloring process. Understanding the effect of alloy types on electrolytic coloring process will enable us to achieve color uniformity and to expand color and shade selections. © 2005 Elsevier B.V. All rights reserved