Oxidation-controlled erosion

A low temperature imparts a metal erosion regime. With increase of temperature this metal erosion regime shifts to an oxide erosion regime via oxidation-affected erosion and oxidation-controlled erosion regimes. 

Schematic presentation of various erosion mechanisms at elevated temperature (a) metal erosion (b) oxide erosion (c) oxidation-affected erosion (d) oxidation-controlled erosion. 

The presence of an oxide scale is responsible for the existence of a variety of material removal mechanisms during elevated temperature erosion of metallic materials. These mechanisms have been carefully verified by experimental work. Four distinct material removal mechanisms, namely metal erosion, oxidation-affected erosion, oxidation-controlled erosion and oxide erosion, have been experimentally established. These experimental observations have been substantiated by theoretical considerations. A suitable criterion for transition from one erosion regime to another regime is yet to evolve. Attempts have been made to analyse such transitions using preoxidized sanities. 

All exposure environments designed to aid in the study of materials degradation in LEO have drawbacks that must be taken into account when trying to interpret either post-exposure analysis data or data collected in situ. Because of the difficulty of controlling an exposure environment, many conclusions about the mechanisms by which atomic oxygen attacks a surface and assists in the oxidation and erosion of materials have been reached less systematically than would be desired. 

A third group includes silver—nickel, silver—cadmium oxide, and silver—graphite combinations. These materials are characterized by low contact resistance, some resistance to arc erosion, and excellent non sticking characteristics. They can be considered intermediate in overall properties between silver alloys and silver or copper—refractory compositions. Silver—cadmium oxide compositions, the most popular of this class, have wide appHcation in aircraft relays, motor controllers, and line starters and controls. 

STABREX is easier and simpler to use compared to any other oxidant available for industrial water treatment. The product is pumped directly from returnable transporters (PortaFeed Systems)17 with standard chemical feed equipment. Previously, the only practical ways to apply bromine were to oxidize bromide solutions on-site with chlorine in dual liquid feed systems, or with one of the solid organically-stabilized bromine products applied from sidestream erosion feeders. The former is cumbersome and complex, and the latter is prone to dusting and difficult to control. Other oxidants require complex handling and feed of toxic volatile gases, unstable liquids, multiple-component products, or reactive solids. Simplicity in use results in reduced risk to workers and to the environment. 

Several application of oxide models have been presented. These included the importance of within-die characterization and prediction for process optimization, and the use of the pattern dependent model in run by ran feedback control. Work has also been done to apply the density model to STI polish. We believe that the generalized framework presented for copper polish is also applicable to the modeling of dishing and erosion in STI CMP. 

A way to further minimize corrosion is by adding base to the feed or reactor, so dial acids formed during the oxidation reaction are immediately neutralized. However, one must then deal with the resulting salts. Whether formed during reaction or already contained in the feed, salts will quickly precipitate in supercritical water. As these salts tend to adhere to and accumulate on the reactor walls and other surfaces within the reactor, they can inhibit and ultimately block process flow unless they are removed or their accumulation is controlled. Nonsalt solids (e.g., metal oxides, grit), by contrast, have little tendency to stick to process surfaces but can be a problem with respect to erosion and system pressure control. Methods that have been developed to manage and/or minimize the impact of corrosion, salt precipitation/accumulation, and solids handling are discussed in Sections 6.5 and 6.6. 

Analyser systems are expensive and should therefore be adequately protected from their environment and the process streams that they control. Every analyser is liable to malfunction upon contact with rain, snow, Ice, wind, sand, dust and so forth. After some time, alternate hot-cold or humid-dry periods cause expansions and compressions that results In erosion and corrosion of the analyser. On the other hand, industrial environments are particularly severe as the rain and atmospheric humidity react with traces of hydrocarbons, sulphurized products and nitrogen oxides to form acids which accelerate corrosion. All these reasons recommend protecting the analyser to an extent depending on the potential hazards of the area where the analyser is... 

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