High-temperature corrosion impurity effects

Addition of about 0 04% arsenic will inhibit dezincification of a brasses in most circumstances and arsenical a brasses can be considered immune to dezincification for most practical purposes . There are conditions of exposure in which dezincification of these materials has been observed, e.g. when exposed outdoors well away from the sea , or when immersed in pure water at high temperature and pressure, but trouble of this type rarely arises in practice. In other conditions, e.g. in polluted sea-water, corrosion can occur with copper redeposition away from the site of initial attack, but this is not truly dezincification, which, by definition, requires the metallic copper to be produced in situ. The work of Lucey goes far in explaining the mechanism by which arsenic prevents dezincification in a brasses, but not in a-/3 brasses (see also Section 1.6). An interesting observation is that the presence of a small impurity content of magnesium will prevent arsenic in a brass from having its usual inhibiting effect . 

The Effect of Aqueous Impurities on the Stress Corrosion Cracking of Austenitic Stainless Steel in High-Temperature Water... 

Fatty Acid Distillation. Distillation of crude fatty acids removes both the low and high boiling impurities as well as odor bodies. Fatty acids are extremely sensitive to heat, oxidation, and corrosion effects. This is due to the reactive acid group at the end of the long carbon chain. These factors are taken into consideration in the design of the distillation unit and its operating parameters. Distillation is carried out under high vacuum and lower temperatures and with the shortest residence time allowable. 

The most direct effect of defects on the properties of a material usually derive from the altered ionic conductivity and diffusion properties. So-called superionic conductors are materials which have an ionic conductivity comparable to that of molten salts. This high conductivity is due to the presence of defects, which can be introduced thermally or via the presence of impurities. Diffusion affects important processes such as corrosion and catalysis. The specific heat capacity is also affected near the melting temperature the heat capacity of a defective material is higher than for the equivalent ideal crystal. This reflects the fact that the creation of defects is enthalpically unfavourable but is more than compensated for by the increase in entropy, so leading to an overall decrease in the free energy. 

Carbon monoxide is a colorless, odorless, flammable toxic gas. Liquid carbon monoxide is a cryogenic liquid, which exists at a temperature of -313°F (-192°C) and atmospheric pressure. It becomes a flammable vapor upon addition of heat. If inhaled, concentrations of 0.4 percent in air prove fatal in less than 1 hour, while inhalation of high concentrations can cause sudden collapse with little or no warning. Pure carbon monoxide has a negligible corrosive effect on metals at atmospheric pressures. Impure carbon monoxide, containing water vapor, sulfur compounds, or other impurities causes stress corrosion to ferrous metals at elevated pressures. 

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