Chemistry has its fair share of visual appeal, and for those who combine their chemical expertise... more Chemistry has its fair share of visual appeal, and for those who combine their chemical expertise with shipwreck conservation, nothing is quite as captivating as a bronze apothecary's mortar.
Publisher Summary This chapter provides an overview of corrosion of metals. It describes the gene... more Publisher Summary This chapter provides an overview of corrosion of metals. It describes the general factors that influence metal corrosion. Over the years, there have been numerous studies on the rates of corrosion of metals in seawater. From various studies, it is now possible to identify the major factors that affect metal corrosion on shipwrecks. These factors are metal composition, water composition, temperature, marine growth, seabed composition, position of objects in relation to other shipwreck components, depth of burial beneath the seabed, and extent of water movement. The combined effect of all these complex and often interrelated factors is that each object must be considered individually when attempting to evaluate its corrosion history or when considering its recovered condition.
The SS Xantho steam engine presented the single biggest conservation problem I've had to solv... more The SS Xantho steam engine presented the single biggest conservation problem I've had to solve. After 25 years of conservation work, the engine was reassembled and is able to be turned over after 112 years of immersion in seawater.
The assessment and treatment of a massive gilded bronze statue on top of the state parliament in ... more The assessment and treatment of a massive gilded bronze statue on top of the state parliament in Wisconsin, USA, by one of my conservation colleagues is a wonderful tale of creative thinking and innovation that is typical of the problems that applied chemists overcome each day. The sculpture was made by Chester French (1850-1931) and had been subjected to various conservation treatments since 1914 when it was first unveiled.
Organic nitriles stabilize acidic aqueous copper(1) sulphate solutions. Electrolysis of such solu... more Organic nitriles stabilize acidic aqueous copper(1) sulphate solutions. Electrolysis of such solutions provides an alternative for the electrowinning and electrorefining of copper. The Cu+/CuO and Cu2+/Cu+ standard reduction potentials in aqueous solutions containing acetonitrile or 3-hydroxypropanenitrile (hydracrylonitrile) differ from those in water, due to the specific solvation and stabilization of the copper(1) ion by either nitrile. In the mixed solvent, the solvation sphere around the copper(1) ion contains organic nitrile, rather than water, and this reduces the mobility of Cu+ and slows its diffusion to the electrode surface in a working cell. The copper(11) ion contains water in its solvation shell in the mixed solvent. Thus for dilute solutions, the diffusion coefficient of the copper(1) ion in 10 mole % aqueous acetonitrile is about two-thirds and in 10% 3-hydroxypropanenitrile-water is about one-fifth that of the copper(11) ion in water. In concentrated solutions containing sulphuric acid, the copper(^^) ion diffuses as ion pairs and this reduces its mobility. This effect is not observed for copper(1) ions. Cell voltages measured during the electrolysis of copper(1) sulphate solutions by using soluble copper, insoluble platinum or insoluble carbon anodes are analysed in terms of the ohmic resistance, the equilibrium potential, the charge-transfer overpotential and the diffusion polarization of the working cell. There is a significant charge-transfer overpotential for the oxidation of Cu+ to Cu2+ at an insoluble graphite anode in 6 mol dm-3 acetonitrile-water solutions; the rate constant is 4 x cm s-'. At platinum the rate constant is 1.6 x l o w 2 cm s-'.
ABSTRACT Marine corrosion has significant economic impacts globally. Marine rust on carbon steel ... more ABSTRACT Marine corrosion has significant economic impacts globally. Marine rust on carbon steel in Western Australia was investigated to determine the importance of various microorganisms in corrosion. Microorganisms were imaged, identified and enumerated by pyrosequencing. The base of tubercles was anaerobic. Pyrosequencing demonstrated the presence of diverse bacteria and archaea. However, the dominant group were methanogenic archaea, representing 53.5% of all sequences. One methanogenic species, Methanococcus maripaludis, comprised 31% of sequences, and can significantly increase corrosion rates by extracting electrons directly from steel. Methanogenic archaea may be significant contributors to marine corrosion of carbon steel.
A series of eleven commemorative 1911 coronation medals struck in Western Australia and manufactu... more A series of eleven commemorative 1911 coronation medals struck in Western Australia and manufactured by Stokes & Company were studied using corrosion potential measurements in 0.1 M sodium chloride to test for debasement of the medals. The falling values of Ecorr indicated that there were a significant number of defects in the surface of the silver medallions and that the different end voltages indicated that the core composition of the medals was not the same. The lowest Ecorr values were associated with a faster rate of falling Ecorr data and these medallions also had lower initial voltages. X-ray fluorescence analysis of both the front and back of the medallions provided chemical composition of the Medals which had been silvered with a silver amalgam before heating. This process left a microporous silver layer which was 8-10 µm which was readily abraded on the high points of the heavily embossed dies.
Abstract: Modelling and electrochemical simulation of corrosion confirms that the decay rate of i... more Abstract: Modelling and electrochemical simulation of corrosion confirms that the decay rate of iron shipwrecks is cathodically controlled by the flux of dissolved oxygen. The rate falls logarithmically with increasing water depth with splash zone corrosion rates at zero water depth. The interaction of corroding iron with the marine biota is complex and symbiotic. Corrosion rates are interdependent on the salinity and temperature of the surrounding seawater which determines the amount of dissolved oxygen. Monitoring the corrosion potentials and pH of wreck materials provides a very sensitive indicator of changes in environment brought about through natural or human intervention.
The partial molal volumes of Na+, Ag+, Cu+, Ph4As+, BPh4-, Cl- and NO3- are reported for transfer... more The partial molal volumes of Na+, Ag+, Cu+, Ph4As+, BPh4-, Cl- and NO3- are reported for transfer from water to various acetonitrile/water (MeCN/H2O) mixtures by using the tatb assumption that ΔVt(Ph4As+) = ΔVt(BPh4-). The results, which show a complex dependence of ionic partial molal volumes on MeCN/H2O solvent composition, are discussed in terms of ion-solvent and solvent-solvent interactions. This study complements earlier work on the energetics of transfer (tatb assumption) of these ions from water to aqueous acetonitrile solutions.
ChemInform Abstract XeF2 in wasserfreiem HF stellt ein mittelstarkes Oxidationsmittel dar, mit de... more ChemInform Abstract XeF2 in wasserfreiem HF stellt ein mittelstarkes Oxidationsmittel dar, mit dem, in vielen Fällen selektiv und schrittweise verlaufend, in grossem Umfang F-haltige Verbindugen dargestellt werden können. Beispiele für die Darstellung von binären und komplexen Fluoriden, Oxidfluoriden und Carbonylfluoriden durch Umsetzung des Difluorids mit Elementen (z.B.
Chemistry has its fair share of visual appeal, and for those who combine their chemical expertise... more Chemistry has its fair share of visual appeal, and for those who combine their chemical expertise with shipwreck conservation, nothing is quite as captivating as a bronze apothecary's mortar.
Publisher Summary This chapter provides an overview of corrosion of metals. It describes the gene... more Publisher Summary This chapter provides an overview of corrosion of metals. It describes the general factors that influence metal corrosion. Over the years, there have been numerous studies on the rates of corrosion of metals in seawater. From various studies, it is now possible to identify the major factors that affect metal corrosion on shipwrecks. These factors are metal composition, water composition, temperature, marine growth, seabed composition, position of objects in relation to other shipwreck components, depth of burial beneath the seabed, and extent of water movement. The combined effect of all these complex and often interrelated factors is that each object must be considered individually when attempting to evaluate its corrosion history or when considering its recovered condition.
The SS Xantho steam engine presented the single biggest conservation problem I've had to solv... more The SS Xantho steam engine presented the single biggest conservation problem I've had to solve. After 25 years of conservation work, the engine was reassembled and is able to be turned over after 112 years of immersion in seawater.
The assessment and treatment of a massive gilded bronze statue on top of the state parliament in ... more The assessment and treatment of a massive gilded bronze statue on top of the state parliament in Wisconsin, USA, by one of my conservation colleagues is a wonderful tale of creative thinking and innovation that is typical of the problems that applied chemists overcome each day. The sculpture was made by Chester French (1850-1931) and had been subjected to various conservation treatments since 1914 when it was first unveiled.
Organic nitriles stabilize acidic aqueous copper(1) sulphate solutions. Electrolysis of such solu... more Organic nitriles stabilize acidic aqueous copper(1) sulphate solutions. Electrolysis of such solutions provides an alternative for the electrowinning and electrorefining of copper. The Cu+/CuO and Cu2+/Cu+ standard reduction potentials in aqueous solutions containing acetonitrile or 3-hydroxypropanenitrile (hydracrylonitrile) differ from those in water, due to the specific solvation and stabilization of the copper(1) ion by either nitrile. In the mixed solvent, the solvation sphere around the copper(1) ion contains organic nitrile, rather than water, and this reduces the mobility of Cu+ and slows its diffusion to the electrode surface in a working cell. The copper(11) ion contains water in its solvation shell in the mixed solvent. Thus for dilute solutions, the diffusion coefficient of the copper(1) ion in 10 mole % aqueous acetonitrile is about two-thirds and in 10% 3-hydroxypropanenitrile-water is about one-fifth that of the copper(11) ion in water. In concentrated solutions containing sulphuric acid, the copper(^^) ion diffuses as ion pairs and this reduces its mobility. This effect is not observed for copper(1) ions. Cell voltages measured during the electrolysis of copper(1) sulphate solutions by using soluble copper, insoluble platinum or insoluble carbon anodes are analysed in terms of the ohmic resistance, the equilibrium potential, the charge-transfer overpotential and the diffusion polarization of the working cell. There is a significant charge-transfer overpotential for the oxidation of Cu+ to Cu2+ at an insoluble graphite anode in 6 mol dm-3 acetonitrile-water solutions; the rate constant is 4 x cm s-'. At platinum the rate constant is 1.6 x l o w 2 cm s-'.
ABSTRACT Marine corrosion has significant economic impacts globally. Marine rust on carbon steel ... more ABSTRACT Marine corrosion has significant economic impacts globally. Marine rust on carbon steel in Western Australia was investigated to determine the importance of various microorganisms in corrosion. Microorganisms were imaged, identified and enumerated by pyrosequencing. The base of tubercles was anaerobic. Pyrosequencing demonstrated the presence of diverse bacteria and archaea. However, the dominant group were methanogenic archaea, representing 53.5% of all sequences. One methanogenic species, Methanococcus maripaludis, comprised 31% of sequences, and can significantly increase corrosion rates by extracting electrons directly from steel. Methanogenic archaea may be significant contributors to marine corrosion of carbon steel.
A series of eleven commemorative 1911 coronation medals struck in Western Australia and manufactu... more A series of eleven commemorative 1911 coronation medals struck in Western Australia and manufactured by Stokes & Company were studied using corrosion potential measurements in 0.1 M sodium chloride to test for debasement of the medals. The falling values of Ecorr indicated that there were a significant number of defects in the surface of the silver medallions and that the different end voltages indicated that the core composition of the medals was not the same. The lowest Ecorr values were associated with a faster rate of falling Ecorr data and these medallions also had lower initial voltages. X-ray fluorescence analysis of both the front and back of the medallions provided chemical composition of the Medals which had been silvered with a silver amalgam before heating. This process left a microporous silver layer which was 8-10 µm which was readily abraded on the high points of the heavily embossed dies.
Abstract: Modelling and electrochemical simulation of corrosion confirms that the decay rate of i... more Abstract: Modelling and electrochemical simulation of corrosion confirms that the decay rate of iron shipwrecks is cathodically controlled by the flux of dissolved oxygen. The rate falls logarithmically with increasing water depth with splash zone corrosion rates at zero water depth. The interaction of corroding iron with the marine biota is complex and symbiotic. Corrosion rates are interdependent on the salinity and temperature of the surrounding seawater which determines the amount of dissolved oxygen. Monitoring the corrosion potentials and pH of wreck materials provides a very sensitive indicator of changes in environment brought about through natural or human intervention.
The partial molal volumes of Na+, Ag+, Cu+, Ph4As+, BPh4-, Cl- and NO3- are reported for transfer... more The partial molal volumes of Na+, Ag+, Cu+, Ph4As+, BPh4-, Cl- and NO3- are reported for transfer from water to various acetonitrile/water (MeCN/H2O) mixtures by using the tatb assumption that ΔVt(Ph4As+) = ΔVt(BPh4-). The results, which show a complex dependence of ionic partial molal volumes on MeCN/H2O solvent composition, are discussed in terms of ion-solvent and solvent-solvent interactions. This study complements earlier work on the energetics of transfer (tatb assumption) of these ions from water to aqueous acetonitrile solutions.
ChemInform Abstract XeF2 in wasserfreiem HF stellt ein mittelstarkes Oxidationsmittel dar, mit de... more ChemInform Abstract XeF2 in wasserfreiem HF stellt ein mittelstarkes Oxidationsmittel dar, mit dem, in vielen Fällen selektiv und schrittweise verlaufend, in grossem Umfang F-haltige Verbindugen dargestellt werden können. Beispiele für die Darstellung von binären und komplexen Fluoriden, Oxidfluoriden und Carbonylfluoriden durch Umsetzung des Difluorids mit Elementen (z.B.
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