Material characteristics aqueous corrosion

The corrosion process also includes acid-base reactions involving solute particles in aqueous solution. As for the acid-base characteristics of corrosion processes, we still have many research issues that remain to be studied, such as the effect of various solutes in aqueous solution on materials corrosion. Novel experimental techniques in the nanometer scale recently developed in electrochemistry and corrosion science will provide, from now on, much information that, we hope, will contribute to elucidating the acid-base characteristics of corrosion processes, particularly the effect of adsorption of solute particles on the corrosion. 

Cobalt. Cobalt is not generally used as a primary alloying element in materials designed for aqueous corrosion resistance. However, cobalt imparts unique strengthening characteristics to alloys designed for high-temperature service. Cobalt, like iron, increases the solubility of carbon in nickel-base alloys, therefore increasing the resistance to carburization. 

Metals. Most metals react with aqueous HCl foUowing equation 22. The reaction rate is dependent on the concentration of the acid, oxidi2ing, reducing, or complexing agents, and corrosion inhibitors, in addition to the metallurgical characteristics of the material and the prevailing hydrodynamic conditions (see Corrosion and corrosion control). 

We have been studying silicon as a PEC cell, partly because silicon would be an exceptionally valuable material for solar cells if the corrosion could be controlled, and partly because the corrosion product, Si02, has particularly simple characteristics it is generally insoluble in aqueous solutions, and it... 

When inorganic chlorides (e.g., ammonium chloride) and organic chlorides collect (usually in the tops of columns and equipment connected to the tops of columns), mild to severe corrosion occurs. When organic nitrogen compounds in the feed exceed 0.05 wt% (500 ppm), cyanides and ammonia form. These compounds collect in the aqueous phases and cause corrosion of certain materials. The corrosion problems in the aqueous phases are discussed in the following section on overhead systems, in the Chapter Two section on characteristics of sour water, and in the Chapter Three section on coolers. 

A hydroxide or carbonate of an alkali metal (e.g., lithium, sodium, potassium, etc), the aqueous solution of which is characteristically basic in chemical reactions. The term may be extended to apply to hydroxides and carbonates of barium, calcium, magnesium, and the ammonium ion. The term alkali should be viewed in relation to the terms corrosive, bases and acids. The EPA defines corrosivity in terms of pH (i.e., wastes with pH <2 or 2.5) or in terms of ability to corrode steel (SAE 20) at a rate of > 6.35 mm (0.250 in.) per year at a temperature of 55° C (13° F). This discussion will address corrosivity as it applies to acids and caustics (i.e., alkali materials). Acids are compounds that yield H ions (actually HjO " ions) when dissolved in water. Common industrial acids include acetic, nitric, hydrochloric, and sulfuric acids. The terms concentrated and dilute refer to the concentrations in solution. Mixing a concentrated acid with enough water will produce a dilute acid. For example, a bottle of concentrated HCl direct from the manufacturer is approximately 12N in HCl, while a solution of HCl used in a titration may be only 0.5N. The latter is a dilute acid solution. 

Evans AG (1972) A method for evaluating the time-dependent failure characteristics of brittle materials - and its application to polycrystalline alumina. J Mater Sci 7 1137-1146 French MA, Pritchard G (1991) Strength retention of glass/carbon hybrid laminates in aqueous media. In Cardon AH, Verchery G (eds) Durability of polymer based composite systems for structural applications. Elsevier Applied Science, New York, pp 345-354 Friedrich K (1981) Stress corrosion crack propagation in glass fibre reinforced/thermoplastic PET. J Mater Sci 16(12) 3292-3302... 

Inhibitors function in one or more ways to control corrosion, namely by adsorption of a thin film onto the surface of a corroding material, by inducing the formation of a thick corrosion product or by changing the characteristics of the environment, resulting in reduced aggressiveness. Some remove oxygen in the aqueous media to reduce the cathodic reaction. Though there are many chemicals that can function as inhibitors, some may be too expensive and not economical. Chemicals that are toxic or not environmentally friendly are also of limited use. Moreover, inhibitors for one metal may or may not work for another or even may cause corrosion. In addition, the effectiveness of inhibitors is affected by the pH, temperature and water chemistry of the system." ... 

For the practical utilization of circulating aqueous slurries, a suitable balance must be made between corrosion-erosion attack of materials of construction and handling properties of the slurry, including viscosity, heat transfer, settling, resuspension, and caking characteristics. The materials of construction, operating conditions, slurry characteristics, and... 

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