Chlorides, corrosive effect

Another method of purifying niobium is by distillation of the anhydrous mixed chlorides (29). Niobium and tantalum pentachlorides boil within about 15°C of one another which makes control of the process difficult. Additionally, process materials must withstand the corrosion effects of the chloride. The system must be kept meticulously anhydrous and air-free to avoid plugging resulting from the formation of niobium oxide trichloride, NbOQ. Distillation has been used commercially in the past. 

A diagnosis of possible damage should be made before beginning repairs with other construction measures [48,49]. There should be a checklist [48] of the important corrosion parameters and the types of corrosion effects to be expected. Of special importance are investigations of the quality of the concrete (strength, type of cement, water/cement ratio, cement content), the depth of carbonization, concentration profile of chloride ions, moisture distribution, and the situation regarding cracks and displacements. The extent of corrosion attack is determined visually. Later the likelihood of corrosion can be assessed using the above data. 

Other polymers can be more troublesome. Poly(vinyl chloride) requires the incorporation of stabilisers and even so may discolour and give off hydrochloric acid, the latter having a corrosive effect on many metals. At the same time some metals have a catalytic effect on this polymer so that care has to be taken in the construction of barrels, screws and other metal parts liable to come into contact with the polymer. 

Mobile-phase selection for cationic polymers is similar to that for the other polymers in that ionic strength and pH can change the shape of the solute from linear to globular (9). Mobile phases are often low pH e.g., 0.1% trifluo-roacetic acid, including 0.2 M sodium chloride, has been used successfully for polyvinylpyridines. Sodium nitrate can be substituted for the chloride to avoid corrosive effects. Some salt must be included so that ion exclusion does not occur (3). 

Other acid gases such as hydrogen chloride and oxides of nitrogen produce similar corrosion problems. The corrosion effects produced by acid condensate are amplified by the motion of the gas stream (typically 20-53 m/s) and erosion effects due to entrained solids and impingement at bends, damper plates, reheaters, etc. 

Sarkar, N. K., Graves, R. A., Park, J. R. and Usha, M. G. Effects of Selected Amino Acids on the Chloride Corrosion of Gold Casting Alloys , Journal of Dental Research, 66, 206 (Abstr. 794) (1987)... 

In marine atmospheres magnesium chloride is formed and eventually oxychloride by reaction with magnesium hydroxide formed at the same time. Since the chloride is hygroscopic, moisture is attracted and the corrosive effect is hence much worse than that of water alone. 

Corrosive wear results from a chemical reaction of the wear surface with the environment. In this section, only corrosion that occurs in conjunction with mechanical wear is considered. Purely corrosive wear is reviewed in Sec. 4.0 below. The chemical resistance of a given coating material must be assessed if the application involves a corrosive environment. A typical example is the environment found in deep oil and gas wells (over 500 m.), which usually contain significant concentrations of CO2, H2S, and chlorides. The corrosive effect of these chemicals is enhanced by the high temperature and pressure found at these great depths. 

See also Lithium compounds Lithium chlorate, 6 117 Lithium chloride, 15 131, 139 corrosive effect on iron, 7 806 dessicant, 8 360 solvent for cotton, 8 21 Lithium chromate, 15 142... 

Potassium chloride, 11 122 12 67 20 611-625. See also KCl-langbeinite ore chemical grades of, 20 62It compaction of, 20 621-625 corrosive effect on iron, 7 806 electrolysis of, 20 633 encapsulated, 16 453 froth flotation of, 20 615-616 mining, 20 613-615 refining, 20 615-621 as salt substitute, 22 819-820 separation from sodium chloride, 20 622 therapeutant for aquaculture in U.S.,... 

Sodium chloride, 22 797-822. See also Salt analytical methods for, 22 811-812 applications of, 22 814-820 from brine, 5 800-801 corrosive effect on iron, 7 806 deposits of, 22 798, 799, 805 described, 22 797 in detergent formulations, 3 418 economic aspects of, 22 810-811 electrolysis of, 22 760 electrolysis of fused, 22 769-772 electrolytic decomposition, 6 175-177 environmental impact of, 22 813-814, 817... 

The quality of the ethanol has a strong influence on its corrosive effects. Three categories of problems have been identified general corrosion (caused by ionic impurities, mainly chloride ions and acetic acid), dry corrosion due to ethanol polarity, and wet corrosion caused by azeotropic water. Corrosion inhibitors should thus be incorporated in ethanol-diesel blends. 

Concretes made with Portland cement have a specific weight of 140 to 150 Ib/ft (2,242 to 2,400 kg/m ). Concrete absorbs the heat of a fire when chemically bound water is released from a crystalline structure and is reduced to lime. Dense concretes can be formed in place, or pneumatically sprayed to the required thickness using steel reinforcement. The corrosive effect of chlorides on the steel surface in moist saline environments (coastal or other chloride environments) dictates the use of protective primers and topcoat sealers. Major advantages of dense concrete are ... 

The porosity of the concrete at an advanced state of maturity is increased in the presence of calcium chloride and, therefore, will allow a greater opportunity for air and moisture to come into contact with the steel reinforcement, encouraging corrosive effects. In practice, with reinforcement cover meeting the relevant codes of practice, this effect is regarded as of minimal significance. 

Although both Fe(III) sulfates and chlorides are effective in coprecipitating As(V) from water, the sulfates may produce less turbidity and corrosion (Han et al., 2003 Floch and Hideg, 2004, 76). As(V) coprecipitation with iron (oxy)(hydr)oxides may be further improved by filtering out the precipitates with membranes or sand. Han et al. (2003) were able to reduce arsenic concentrations to below 2pgL-1 with Fe(III) doses of 6 mgL-1 followed by membrane filtration (Table 7.1). Using Fe(III) sulfate coprecipitation followed by sand filtration, Yuan et al. (2003) found that 0.25 mM of Fe(III) could inexpensively remove about 98 % of 1 mgL-1 of As(V) from household water supplies. Dosages of aluminum sulfate (0.25 mM as Al(III)) achieved about 95 % arsenic removal. 

Toxicity and health effects Exposure to hydrogen chloride causes irritation and corrosive effects to the tissue on contact. Acute exposure to low concentrations of hydrogen chloride causes throat irritation, and prolonged exposure... 

SAFETY PROFILE Confirmed carcinogen with experimental tumorigenic data by skin contact. Human systemic effects by inhalation unspecified effects on olfaction and respiratory systems. Corrosive effects on the skin, eyes, and mucous membranes by inhalation. Flammable when exposed to heat or flame. Will react with water or steam to produce heat and toxic and corrosive fumes. Violent or explosive reaction with dimethyl sulfoxide, and aluminum chloride + naphthalene. To fight fire, use alcohol foam, CO2, dry chemical. Incompatible with dimethyl sulfoxide, (NaNs + KOH), water, steam, and oxidizers. When heated to decomposition it emits toxic fumes of CT, See also CHLORIDES and ALDEHYDES. 

In contrast to the classification of Dangerous Substance Directive 67/548/EEC, a corrosive effect has to be tested on animal skin and additionally at metallic surfaces. As a consequence, many salts are classified in Class 8 in accordance with the ADR regulations but have no corrosive property at the skin. Prominent examples are halogenide compounds, e.g., sodium chloride. 

Modern pressure-absorption s retems permit absorption efficiencies of more than 99% and acid concentrations in the range of 55% to 65% to be obtained. In some processes, concentrations of up to 70% HNO3 are achieved by using high pressures and cooled water in conjunction with specially designed absorption columns. In some plants, excess air may be injected into either the cooler or absorption column to speed the oxidation reaction. Process water for absorption systems must be very pure to reduce corrosion effects in the nitric acid plant and also in applications involving subsequent use of the acid. In particular, the chloride content must be very low. Hence, water from condensate sources or ion-exchange purification units is often used. 

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