The valuable properties of silver can be diminished or destroyed because the metal is susceptible to corrosion by certain atmospheric species. Particularly aggressive is H<SUB>2</SUB>S which 'tarnishes' the surface by reacting to form Ag<SUB>2</SUB>S. There have been many attempts in the past to produce a tarnish resistant silver either by surface coating or bulk alloying; none have so far proved to be entirely successful. This thesis describes the production of surface coatings on silver by inert and reactive sputtering for application in the Silversmithing Industry. They should, therefore, be indistinguishable from silver and contain no more than 7.5% (by weight) of alloying addition (to comply with the Sterling Standard). Initially, the tarnish behaviour of uncoated pure and Sterling silver was investigated. Results indicated that the degree of sulphidation is a strong function of alloy content and also of surface preparation. Oxides of tantalum, hafnium, niobium, tin, zirconium, yttrium, titanium and aluminium were produced by reactive sputtering and deposited onto sputtered silver substrates. Films were characterised by X-ray diffraction and tarnished in a controlled atmosphere. The degree of sulphidation was then assessed by Energy Dispersive X-ray Analysis. The protectiveness of the oxide films was related to film stress, thickness and sputter deposition conditions. Using a dual-target sputter system, alloys of silver-tantalum, silver-hafnium, silver-niobium, silver-titanium and silver-aluminium were produced. The tarnish behaviour of the alloys was investigated as a function of alloy composition. X-ray diffraction analysis demonstrated that the deposition technique was capable of producing non-equilibrium structures. For some of the alloys, selective oxidation resulted in a slight improvement in tarnish resistance. In order to establish whether selective oxidation might produce completely protective surfaces, further studies of the oxidation of such materials needs to be undertaken.

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D. Tech. Chemical, Metallurgical and Materials Engineering / Corrosion is the chemical or electrochemical interaction between a material, especially metals, and their environment resulting in mild to severe deterioration of the material and its properties. The economic impact and problems resulting from corrosion has drawn strong attention from scientists and engineers worldwide. Stainless steel is the most important engineering metal worldwide, and industrially stainless steel is used extensively due to its resistance to corrosion e.g. in acid pickling, industrial acid cleaning, acid descaling, oil well acidizing and the petroleum industry. The corrosion resistance of stainless steels is due to the formation of a protective film which covers the steel surface instantaneously when exposed to mild operational conditions in the presence of oxygen; however, the oxide is most often porous and insufficient to protect the steel from further oxidation and corrosion attack in harsh environments. It is hypothesized that: In-depth understanding of the electrochemical behaviour of ferrous alloys in interaction with selected organic compounds in acidic environments will enhance inhibitor application for corrosion control; Failure and poor performance of most inhibitor admixtures can be eliminated with comprehensive knowledge of electrochemical interaction at the metal-inhibitor interface, passive film formation, duration and breakdown, adsorption characteristics, bond formation and molecular structure effect; Optimization of the current electroanalytical method will enhance effective pitting corrosion detection, analysis and control with the use of organic inhibiting compounds. The primary aim of this research is to develop the science required for the effective assessment, development and confident use of organic compounds (heterocyclic compound, organosulphur compound, simple alcohol, aromatic amine compound, aromatic amine derivative and aminoalcohol) and tested alloys (austenitic stainless steel type 304 and mild steel) for applications in astringent environments through conventional and optimized corrosion monitoring techniques.

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Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 113-114). / xi, 132 leaves, bound ill. 29 cm

The Center for Ocean Energy Technology at Florida Atlantic University is developing an ocean energy turbine system to investigate the feasibility of harnessing Florida's Gulf Stream current kinetic energy and transforming it into a usable form. The turbine system has components which are prone to marine corrosion given the materials they are made of and to the harsh environment they will be exposed to. This study assumes a two-part system composed of a coating system acting as a barrier and sacrificial anode cathodic protection which polarizes the metal structures to a potential value where corrosion is significantly reduced. Several configurations (varying in anode quantity, size and location) were considered in order to cathodically protect the structures with various coating qualities (poor, good and excellent). These cases were modeled and simulated via Boundary Element Method software and analyzed so as to assess the most appropriate design. / by Nicolas Gantiva. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

A fundamental study was conducted to investigate the ability of thin polymeric coatings to prevent metallic contact and fretting corrosion in steel-on-steel systems. Ten polymer types were chosen for study: polymethylmethacrylate (PMMA), polytetrafluoroethylene (PTFE), polyimide (PI), polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), low-density polyethylene (LOPE), high-density polyethylene (HDPE), polysulfone (PSO) and polystyrene (PS). These polymers were applied as thin films to a steel disk which was in turn fretted by a normally-loaded steel sphere. The experimental investigation consisted of two phases. In the first phase, the lives of the ten polymer types were evaluated over a range of normal loads from 11.1 to 44.5 N. In the second phase, optical and electron microscopy were used to document the fretting process at the sphere-film interface as a function of time. / Master of Science

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<p dir="ltr">This study aims at summarizing the state-of-the-art on types and use of coated reinforcing steel with special focus on fusion bonded epoxy coatings. It provides INDOT with an overview of the current research and practice on durability and performance of epoxy-coated and stainless-steel cladding reinforcement. It also provides a summary of USDOT practices related to corrosion protection systems. This information is compiled to assist INDOT in the evaluation of epoxy-coated reinforcement against the use of other alternatives for use to protect concrete bridge decks against corrosion of reinforcement under the current practice of deicing salts in Indiana.</p>

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