Oxygen construction materials

Corrosive species in the atmospheres include water, salts and gases. Clean atmospheres contain little other than oxygen, nitrogen, water vapor and a small quantity of carbon dioxide. These species are virtually non-corrosive to any of the common constructional materials for plant at normal temperatures. Steel is susceptible to corrosion in even fairly clean air where water can exist as liquid. For plant operating at temperatures up to approximately 100°C coatings are employed to protect steel if required. In clean air corrosion rates are low, and corrosion is primarily a cosmetic problem, although it may be necessary to prevent mst staining of nearby materials. 

Copper alloys such as brass and bronze, which are harder and more resistant to corrosion than is copper, are important construction materials. Copper corrodes in moist air in the presence of oxygen and carbon dioxide ... 

Oxygen compounds of silicon constitute three fourths of the earth s crust. In practically all rocks and minerals as well as constructing materials based on silicon, the element is present in a tetra-covalent state. Due to its electron-acceptor ability, however, a silicon atom can be five-, six-, and, possibly, even seven-coordinate. 

This group of materials encompasses some of the most widely used construction materials as it includes steels and stainless steels. In pharmaceutical process applications, low-alloy steels are typically limited to structural uses and see little contact with product. Mild steels have been utilized successfully in stills, provided the oxygen content is maintained at very low levels. Tool and die steels may be used in areas where the product is dry and no corrosion is anticipated. 

The use of dirty commercial fuels plus C02-containing air—as opposed to pure hydrogen and pure oxygen used on spacecraft—made the useful life of fuel cell systems (using construction materials commercially available at the time) too short for economical operation. 

This step in the process presents very severe corrosion conditions since die apparatus parts are subjected to the action of a hot, acid solution saturated with oxygen. Such materials of construction may only be used as will insure a satisfactory equipment life and a product free from contamination by corrosion products. 

Essentially three reactor concepts were developed and studied [93-99] tubular reactor (e.g. [93-95]), tank reactor with the reaction zone in the upper part and a cooling zone in the lower part of the tank to dissolve the salts (e.g. [96]), and the transpiring wall reactor with an inner porous pipe which is rinsed with water to prevent salt deposits on the wall (e.g. 94, 97-99]. A fourth concept is the hydro-thermal burner, which cools the wall by coaxial injection of large amounts of water [100]. As oxidants, mainly air, oxygen, and hydrogen peroxide were tested. Mostly Ni-based alloys were used as reactor construction materials. 

Titanium aluminide alloys based on Ti3 A1 and TiAl are of interest as construction material for high temperature components particularly in aerospace industry. Good mechanical properties can be attained with alloys consisting of y-TiAl with 3 to 15 vol% a2-Ti3Al. The disadvantages are the low ductility and the inadequate oxidation resistance at service temperatures of 700-900°C [1]. A fundamental understanding of the oxidation behaviour is necessary in order to improve the corrosion resistance. The formation of the oxides on the alloy surface depends on the temperature, the oxygen partial pressure of the corrosive atmosphere, and the thermodynamic activities of Ti and A1 in the alloys. 

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