Marine environment generally

In summary, silicon caibide/aluminum MMCs are susceptible to localized corrosion in marine environments. Generally, the susceptibility to pit initiation is similar for conposites and uiueinforced alloys however, the rate of pit propagation is higher for composites. Silicon catbide/aluminum corrosion in seawater is increasingly more severe than in the other marine environments. Corrosion-resistant coatings are recommended for these composites to enhance their service lives. 

The ocean is host to a variety and quantity of inorganic raw materials equal to or surpassiag the resources of these materials available on land. Inorganic raw materials are defined here as any mineral deposit found ia the marine environment. The mineral resources are classified generally as iadustrial minerals, mineral sands, phosphorites, metalliferous oxides, metalliferous sulfides, and dissolved minerals and iaclude geothermal resources, precious corals, and some algae. The resources are mosdy unconsoHdated, consoHdated, or fluid materials which are chemically enriched ia certain elements and are found ia or upon the seabeds of the continental shelves and ocean basias. These may be classified according to the environment and form ia which they occur (Table 1) and with few exceptions are similar to traditional mineral deposits on land. 

Remarkably little has been published on corrosion fatigue crack propagation in copper and its alloys. In general little or no influence of marine environments has been observed in crack propagation experiments on manganese and nickel-aluminium bronzes although the frequencies employed were quite high (> 2.5 Hz) ... 

Concrete exposed to deicer salts, or to a marine environment is subjected to chloride and sodium loading. The ability of concrete to resist the penetration of chlorides and sodium is a primary design consideration in marine or cold environments. The ingress of chlorides into concrete is a major problem due to chloride-induced corrosion of the reinforcing steel and deicer salt scaling [a process by which a thin layer (< 1 mm) of concrete deteriorates from the surface of the concrete]. The penetration of sodium from sea water or deicer salts is generally... 

While a great many compounds that have been or might be found in the marine environments have been accused of chelation, this section deals only with the nonspecific measurements of chelation, with what has been called chelation capacity . In general, this capacity is measured by spiking the solution with a transition metal, preferably one that is easily measured, and then determining either how much is complexed or how much is left over. While the principle of all of the methods is the same, the details are different, and often quite ingenious. 

Although the marine environment can generally be considered the final destination of industrial and urban wastewater effluents, studies of biodegradation of linear alkylbenzene sulfonates (LAS) in this compartment have been scarce until recently [1—8]. The removal of LAS from the marine medium seems to be an efficient process, as shown by the low levels of LAS detected in samples of both water and sediment [9—11]. High values have only been found in zones close to the direct wastewater effluent discharge points of urban areas [11]. 

The fate of organic matter in the marine environment is largely related to its molecular structure, as this determines chemical reactivity. Compoimds characterized by high concentrations in seawater and the sediments typically have slow loss rates relative to their production. These compounds tend to exhibit low chemical reactivity in the marine environment and can persist in seawater fiar thousands of years. Conversely, compounds with low concentrations typically have high loss rates relative to their production. Their high reactivity is generally due to rapid biotic uptake and transformation, leading to turnover times that are on the order of minutes to days. Thus, to imderstand... 

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