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No description available.

The purpose of this investigation was to determine the corrosion characteristics of Incoloy alloy 825 in 1.0 to 15.0 normal sulfuric and 0.5 to 3.0 normal hydrochloric acids at 25 to 60°C in both nitrogen-saturated and air-saturated acids, using potentiostatic polarization techniques. Anodic polarization curves were obtained by changing the potential of an Incoloy 825 test electrode and measuring the resulting current. In both acids, there is no difference in the polarization characteristics in air-or nitrogen-saturated solutions. In 1.0 to 15.0 normal sulfuric acid at 25 to 60°C, the alloy spontaneously passivates and does not exhibit a significant active region. In 0.5 normal hydrochloric acid at 25°C, Incoloy 825 is spontaneously passive, but is active at higher concentrations. At 25°C, as the hydrochloric acid concentration increases from 1.0 to 3.0 normal,the critical current density increases from 260 to 5900 microamperes per square centimeter. At 40°C, as the acid concentration increases from 0.5 to 2.0 normal, the critical current density increases from 25 to 28,000 microamperes per square centimeter. In 1.0 normal hydrochloric acid at 25°C, the corrosion rate calculated by weight loss measurements for potentiostatically controlled Incoloy 825 agrees closely with the corrosion rate calculated from polarization current densities, and indicates that the elements dissolve in the proportions present in the alloy. Potentiostatically passivated Incoloy 825 in 1.0 normal hydrochloric acid at 25°C does not exhibit a stable passive condition, reverting to the active state in less than 12 hours. / M.S.

Reinforced concrete exposed to chlorides is subject to rapid deterioration once the concentration of the chloride ion in the concrete reaches a critical level to cause corrosion of the reinforcing steel. The chloride ion diffuses through concrete according to Fick's Law, which is a function of time, a driving concentration, and a diffusion constant. The diffusion constant varies with temperature and the variety of concrete . The research included determination of diffusion constants for six types of concretes after 8 weeks and 16 weeks of ponding with an NaC1 solution. In addition, one set of these samples was subjected to the outside environment while the other was indoors under controlled conditions. The mixes included water to cement ratios of 0.35, 0.40, 0.45, and 0.50, and two water to cement ratios of 0.45 with 15% cement replacement with pozblan admixtures (silica fume and type'F flY ash). Thus, the effects of temperature, water to cement ratio, and pozzolanic admixtures in regard to the diffusion constant for concrete were found. The method by,which a diffusion constant was found is as 1)X3% solution of-NaC1 is ponded on top of a four inch thick 'specimen of concrete. 2) Powder samples of the paste are taken at specified time at depths of -0.5, 1.0 1,:5, and 2-.5 inches. 3) These samples are analyzed for chloride content by potentiometric titration. 4) The data is fit to Fick's Law by nonlinear regression and an effective diffusion constant determined. / Master of Science

A statistical analysis was conducted to investigate the effect of applied load and relative humidity of the atmosphere on the durability and coefficient of friction of five polymer coatings used to protect against fretting corrosion. Chlorine and non-chlorine containing polymers were used in this research to see if the large humidity effect seen in a previous study with polyvinyl chloride is strictly a chlorine related phenomenon. The five polymers used were polyvinyl chloride, polyvinylidene chloride, polystyrene, and two siloxane modified polyimides. Disks made of 1045 steel were coated with thin polymeric films and fretted against a 52100 steel ball. Three levels of load were used: 11.12, 22.25, and 44.5 N, and the two levels of relative humidity were less than 10% and between 45 and 55%. Amplitude of oscillation was 330 μm peak to peak, frequency of oscillation was 40 Hz, and the coating thickness was 25 μm. Statistically significant variables and interactions are identified, and reasons for their significance are discussed. Increasing the humidity had no consistent effect on the ending coefficient of friction between the polymer film and the oscillating ball, increasing the load decreased the coefficient of friction, and either increasing the humidity or load decreased the life of the coating during fretting. The extent of this reduction in life depends on the polymer. The relative humidity of the environment affected the coating life of only one of the chlorine-containing polymers. Humidity was also shown to affect the coating life of two polymers that do not contain chlorine. / Master of Science

The main purpose of this research is to determine if polymer films can prevent fretting between two metals, and if they can, what the protection mechanisms are. This research is a part of fretting corrosion studies currently funded by the Army Research Office. Four thermoplastic polymers were tested for their effectiveness. Two other independent variables were also tested: plate hardness and plate roughness. A ball-on-plate device was built to approximate point sliding at the fretting corrosion interface. The tribometer has two experimental positions that are electrically insulated from the rest of the apparatus so that an electrical circuit could be used to monitor metal-to-metal contact. All experiments were run with 52100 steel balls, 1040 steel plates, a normal load of 45 N (10 lbf), an amplitude of .33 mm (.013 in.) and a frequency of 20 Hz. PVC films were found to prevent fretting and metallic contact for 40 minutes. An electrochemical fretting corrosion mechanism has been suggested to explain this behavior. PTFE, LDPE, and PSF films could all produce fretting corrosion while preventing metal-to-metal contact for 40 minutes. Plate hardness and plate roughness had no statistical significance on the measured minimum fretting friction force. / M.S.

This investigation was undertaken in order to determine the effect of alloying on the corrodibility of various alloys to hot crude tallow. / Master of Science

This thesis presents both an analytical and an experimental evaluation of the feasibility of using infrared thermographic techniques to detect subsurface damage in concrete. Various methods of artificial heating, required to effectively apply this technique, are presented. Four major conclusions are reached in this study. 1) Normal ambient diurnal atmospheric temperature changes are not generally sufficient to produce a measurable response in bridge substructures. 2) Heating by an infrared heat source is a technically viable artificial method provided some type of surface preparation is made to assure uniform emissivity. 3) Hot air heating is a viable technical alternative which does not require surface preparation prior to the application of heat. However, this method does require some type of enclosure to produce a hot air pocket. 4) Artificial heating methods based on heating blankets are not a feasible method due to local nonuniform heating effects. / Master of Science

No description available.

No description available.