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Dissertation (Ph.D.)--Auburn University, 2009. / Abstract. Includes bibliographic references (p.111-118).

No description available.

The railroad industry plays a pivotal role in commerce and greatly impacts America's economy. With this in mind, they cannot afford downtime or service interruptions due to bridge or member replacement. Corrosion of bridges causes millions of dollars each year for the railroad industry in terms of maintenance and inspection. Since a large number of these bridges are steel and their service life is typically governed by fatigue of welded details, it is important to determine the interactions of the corrosion and fatigue mechanisms. While there are differing opinions on the effects of corrosion on the fatigue life of welded steel attachments, the intent of this research is to experimentally investigate the relationship between fatigue and corrosion and determine whether this relationship is beneficial, neutral, or detrimental to the fatigue behavior of welded attachments. In order to investigate the effects of corrosion on the fatigue life of welded steel attachments, a testing methodology simulating the conditions a bridge could be expected to experience during its service life is established, executed and the results evaluated. Thirty-two specimens were subjected to cycles of corrosion and interval fatigue loading at varying corrosion times and fatigue cycles. These corrosion-fatigue specimens were then compared to the five control (non-corroded) control specimens and three pre-corroded specimens. The results show that the fatigue life of welded steel attachments is not decreased by the effects of corrosion until more than half of the cross section has been reduced. Specimens subjected to a 'pre-corrosion' period occurring in the absence of fatigue loading, then subjected to cyclic fatigue loading at a later time have drastically reduced fatigue lives.

Abstract The objectives of this thesis are to investigate the microstructures and the corrosion resistance of chromium (Cr) and nichrome (Ni-Cr) thin films deposited by rf magnetron sputtering. Different rf powers were used to prepare the Cr thin films on glass substrates. The thin films were then patterned and subsequently annealed in vacuum environment. The targets used for the sputtering are commercially available Cr and nichrome with 4N and 99.95% purity, respectively. Two different nichrome targets were used. The composition of Ni in nichrome are 40 and 80%. The sputtered samples were etched by reactive ion etching in a mixture of SF6 and O2 for testing the corrosion resistance of the deposited films. The thin films with excellent surface morphology and corrosion resistance can be obtained by preparing the films at a low rf power. This is because the films had lower stress and less defects than the films prepared by high rf powers. At a low power of 20W, the etching rates as low as 120Å/min and 50 Å/min for Cr and nichrome were achieved. The annealing effect of the deposited films at different temperature are also discussed.

Thèse--Université de Paris VII, 1973. / Bibliogr. p. 110-111.

Thèse doctorat : Génie des Matériaux : Villeurbanne, INSA : 2004. / Titre provenant de l'écran-titre. Bibliogr. p. 200-207.

Thèse de doctorat : Chimie et science des matériaux : Paris Est : 2008. / Titre provenant de l'écran-titre.

At Forsmark, several cases of suspected galvanic corrosion have been detected and believed to be caused by an inappropriate use of graphite gaskets in brackish water. This report studies the likelihood of galvanic corrosion between the graphite gasket and stainless steels and aims to be a reference when investigating galvanic corrosion in the future. To evaluate galvanic corrosion, several electrochemical experiments were studied, such as galvanic series, polarization curves, and galvanic current measurements with a ZRA. The electrochemical results showed that when immersing the stainless steel (254 SMO) and the graphite gasket (Novatec) into brackish water, there was a current flowing between the electrodes. However, the current was very small, which could be explained by the protection from a passive film on the stainless steel. The difference in corrosion potential between the two materials was measured and compared to results from polarization curves. It appeared that 254 SMO would be protected by a passive film at the measured potential. Galvanic current measurements also indicated the presence of a passive film under the investigated conditions. The results indicate that galvanic corrosion itself should not have caused the corrosion attacks at Forsmark. The found corrosion is more likely due to crevice corrosion that was accelerated by the combination of a crevice, a welded flange surface, chlorides in water and possibly a graphite gasket.

Corrosion and inhibitor protection of mild steel specimens immersed in acid chloride solution was investigated at ambient temperature by gravimetric and potential monitoring methods. The electrode potential monitoring was performed using a digital voltmeter and a saturated calomel electrode (SCE) as the reference electrode. Extracts of kola plant and tobacco in different concentrations were used as ‘green’ inhibitors. This paper reports the results obtained from the weight loss method, calculated corrosion rates and the observed electrochemical response from the electrochemical potential monitoring of the mild steel during the experiments. A reduction in the active corrosion reactions behaviour of the mild steel test specimens in the strong acid chloride was obtained with the addition of different concentrations of the plants extracts. There was a drastic reduction in the weight loss and in the corrosion rate of the test samples. This behaviour was attributed to the protective film provided on the steel’s surface by the complex chemical constituents of the plants extracts. Effective protection of the mild steel was achieved in nearly all the extracts for the greater part of the experimental period. However, the most effective results were obtained from the tobacco extract and also from the extract of kola leaf.