Project report (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaf 152). Also available via the Internet.

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This thesis describes an investigation of corrosion processes occurring under thin polymeric layers (3 -5 mum) and suggests ways by which the films suppress the onset of corrosion of the bulk metal in corrosive aqueous environments. Synthetic solutions have been developed which replicate pH and conductivity conditions, likely to be found in beverage cans and which have been used to conduct corrosion studies of commercial lacquer systems. Studies carried out highlight the following points: i) The degree and nature of the film cross-linking has a role in the anti-corrosive action of the films. ii) The quantity of iron released into the beverage is much lower than expected when the corrosivity of the solution and the relative thinness of the film are considered. Work carried out indicates a possible means by which the iron might be complexed by the phenolic cross-linker component of the film with evidence having been obtained showing the ease with which phenolic cross-linker/iron complexes can be formed. iv) Optical Emission Glow discharge spectrometry has provided evidence that iron corrosion products are trapped within the polymer matrix. The work has also highlighted a means of accurately determining the film thickness. v) Water permeation across the cured films was followed using infra-red spectroscopy. The amount of water at found to migrate across films of different cross-linking densities was observed to vary with phenolic cross-linker level present vi) Permeation of ions across cured films has been followed with the use of ion selective electrodes. The films have also been shown to be perm-selective towards the diffusion of sodium ions in preference to chloride ions, in aqueous sodium chloride solutions, thus exhibiting a duality in the nature of the coatings towards the constituents of corrosive environments. vi) Alternating Current Impedance spectroscopy, has been used to observe the electrolyte penetration and corrosion initiation processes, in situ. A knowledge of the electrochemical processes occurring for these water-based epoxy-acrylate films during electrolyte penetration, saturation of the film and development of corrosion underneath the film has been obtained.

Master of Science

The Painter’s Wife and Other Stories is a novella and a collection of short fiction focusing on the lives of women and men in the contemporary Western United States. In their exploration of Western life, the novella and short stories subvert the popular mythology of the West. The novella and stories are set in one of three Colorado settings: the city of Denver, the rural Western slope, and the mountain communities of the Western Slope. Beyond being linked by region, the stories are also loosely linked by characters. Characters from one story are mentioned or make brief appearances in others, reinforcing the idea of a people connected by community and landscape.

The Painter’s Wife and Other Stories is a novella and a collection of short fiction focusing on the lives of women and men in the contemporary Western United States. In their exploration of Western life, the novella and short stories subvert the popular mythology of the West. The novella and stories are set in one of three Colorado settings: the city of Denver, the rural Western slope, and the mountain communities of the Western Slope. Beyond being linked by region, the stories are also loosely linked by characters. Characters from one story are mentioned or make brief appearances in others, reinforcing the idea of a people connected by community and landscape.

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Masters of Science / Nampak packages millions of cans a year and a very small percentage of these cans fail due to many reasons. One of the main reasons that cause 2- piece food cans to fail is split flanges. Split Flanges arises due to a number of reasons which will be discussed in detail.The focus of this thesis was based on the causes of split flanges in 2-piece food cans. A study on manufacturing the steel and can making together with packaging fish in these cans was conducted. Another study on the reasons for split flanges occurring in 2 piece cans was conducted done as well.The purpose of the investigation was to check if hydrogen embrittlement could be the cause for split bodies forming in 2 piece food cans. 2 piece cans are drawn and wall ironed from tinplate; the cans were made up of a top and a shaped body. It was this shaped body that went through a considerable amount of stress during manufacture especially at the top of the can, which gave an explanation to why the cans split at the curved area near the flange of the can.According to previous studies done at Nampak R&D more complaints about split bodies were coming from the Fish canneries on the West Coast than the Vegetable canneries. These canneries used the exact same cans to package their product. The difference between the processes at these canneries was the exhaust boxes at the fish canneries. The exhaust box is a long tunnel filled with steam used to precook the fish; the vegetables are not precooked in exhaust boxes. Non metallic inclusions (NMI) was one of the main reason for these split flanges to occur and a reason of particular interest in this research.NMI’s were distributed throughout the steel of the cans and since the same cans were used for the fish and vegetable canneries, they should be failing at the same rate. Yet only complaints came from the fish canneries. So the primary focus of the research was to check if the additional steam process contributed to the formation of split bodies / flanges. We proposed to investigate if hydrogen atoms collect at grain boundaries, vacancies and non metallic inclusions and also to check if the steam accelerated embrittlement. Hydrogen is believed to penetrate right into the bare steel of the cans that were exposed to steam.Hydrogen atoms are being investigated because of their small size, their ability to diffuse through a metal lattice and form hydrogen molecules within the intermetallic vacancies of the metal. The molecules of hydrogen, once formed within the internal structure of the metal, remain trapped because of their larger size and can generate a significant pressure that can contribute to the formation of split bodies. [1] The first step to prove whether H-embrittlement was present in the cans was to check if hydrogen was present. A spectroscopic method namely, elastic recoil detection analysis (ERDA) was used to check if H could be detected using the Elastic Recoil Detection Analysis technique. Several experiments were designed to make sure the technique was suitable for the detection of H. Even though it is known that all metals are susceptible to corrosion and Hembrittlement, the tinplate metals had to be checked in an environment similar to the exhaust box (suspected area causing hydrogen embrittlement) in the factories.Further characterization was done using X-Ray Diffraction to measure the residual stress and relate it to the effects of H-embrittlement. If the H had penetrated into the metal it would cause some distortion in the atomic distances between the atomic planes in Fe atoms and can be measured using XRD.Another effect of hydrogen embrittlement is to reduce the strength in the metal. Tensile tests were performed to measure the strengths of the metal.

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