Chloride contamination

Contamination Chloride ions can leach out through the SCE sinter... 

To study the effect of contaminants (chlorides and sulphates) at the interface metal/coating, a set of panels (surface A Sa 3) was prepared and dosed with solutions of NaCl and FeSO in distilled water and methanol. Subsequently, two paint systems (chlorinated rubber and polyurethane) were applied on these contaminated surfaces. 

M) or chloride ions (o) vs. pH. o chloride contamination, chloride-free hematite (Matijevic, 1980, with permission). 

Salt Contamination (Chlorides) Surfactants are available to effectively maintain stable foam in saturated aqueous solutions. An example application is using foamed saturated brine to drill through troublesome salt sections. 

EfKirts are underway to improve the water quality in the K-, L-, and P-Reactor Disassembly Basins which should reduce the initiation of new pits but may not slow the corrosion at current pits. At current levels of chlorides and conductivity (approximately 6 to 20 ppm and 135 rmho/cm, respectively), corrosion of aluminum cladding is almost certain as discussed in References 8-, . 8-61, and 8-62. Experience with lower levels of contaminants (chlorides in the ppb range and conductivity < 1 pmho/cm) shows aluminum-clad fiiri can be stored4br more than 10 years without signs of corrosion. 

Corrosion tests for hydraulic brake line fluid, as well as for motor oil, grease, and lubricants, are listed in Table 12. In addition, the effects of various fuels on materials have been of importance due to the effect of small amounts of water, which can become trapped in eureas such as the fuel tank [57]. Various additives to fuels can prevent corrosion effects and include inhibitor packages and small amounts of alcohol and aromatics. Recently, corrosion testing of ethanol fuels has been of interest because small amounts of water as well as other contaminants (chlorides) cause severe corrosion to occur [55]. Tests for fuels include electrochemical polarization and immersion tests (Table 12). 

Hull Cell. Operation at 2 A will show the presence of organic contamination, chloride concentration, and overall bath condition. However, an optimnm Hnll cell panel is only a small indication that the bath is in good operating condition, since test resnlts are not always related to production problems. More reliable resnlts are obtained by adjnsting the bath before Hull cell testing. See Sec. 29.12.4 for procednres on Hnll cell. 

Chlorates are easily prepared by electrolyzing a hot chloride solution in a cell without a diaphragm. Repeated crystallization separates the chlorate from any contaminating chloride. 

In early designs, the reaction heat typically was removed by cooling water. Crude dichloroethane was withdrawn from the reactor as a liquid, acid-washed to remove ferric chloride, then neutralized with dilute caustic, and purified by distillation. The material used for separation of the ferric chloride can be recycled up to a point, but a purge must be done. This creates waste streams contaminated with chlorinated hydrocarbons which must be treated prior to disposal. 

The measurement of chlorides is standardized (NF M 07-023, ASTM 3230) the result of two measurements is expressed in mg of NaCl/kg of crude. Table 8.14 gives the contents of some crude oils these values come from measurements taken in a refinery and thereby include the salts brought in by contamination. 

While with-in the mobile x-ray system, the waste in the sampler, is contained within a replaceable (and disposable) polyvinyl chloride (PVC) sleeve with a wall thickness of approximately 0.2-inches and a sealed bottom. It was anticipated that the PVC tube or sleeve would, with use, become highly contaminated with waste residues which drip of fall-off the sampler. The sleeve is coated with a conductive coating to prevent static electricity buildup . There are no sources of ignition in this sealed spare. The sampler (and waste) is coupling which includes a positive pressure gasket. This barrier is further isolated by a second barrier consisting of an epoxy coated aluminum sleeve also sealed-off from the main x-ray cabinet and PVC sleeve. There are also no potential sources of ignition in this isolated secondary space as well. 

Nitrobenzene. Nitrobenzene, of analytical reagent quality, is satisfactory for most purposes. The technical product may contain dinitrobenzene and other impurities, whilst the recovered solvent may be contaminated with aniline. Most of the impurities may be removed by steam distillation after the addition of dilute sulphuric acid the nitrobenzene in the distillate is separated, dried with calcium chloride and distilled. The pure substance has b.p. 210°/760 mm. and m.p. 5 -7°. 

The high sodium ion concentration results in facile crystallisation of the sodium salt. This process of salting out with common salt may be used for recrystallisation, but sodium benzenesulphonate (and salts of other acids of comparable molecular weight) is so very soluble in water that the solution must be almost saturated with sodium chloride and consequently the product is likely to be contaminated with it. In such a case a pure product may be obtained by crystallisation from, or Soxhlet extraction with, absolute alcohol the sul-phonate is slightly soluble but the inorganic salts are almost insoluble. Very small amounts of sulphones are formed as by-products, but since these are insoluble in water, they separate when the reaction mixture is poured into water ... 

Health and Safety Factors. Although butynediol is stable, violent reactions can take place in the presence of certain contaminants, particularly at elevated temperatures. In the presence of certain heavy metal salts, such as mercuric chloride, dry butynediol can decompose violently. Heating with strongly alkaline materials should be avoided. 

Brine Preparation. Sodium chloride solutions are occasionally available naturally but they are more often obtained by solution mining of salt deposits. Raw, near-saturated brines containing low concentrations of impurities such as magnesium and calcium salts, are purified to prevent scaling of processing equipment and contamination of the product. Some brines also contain significant amounts of sulfates (see Chemicals FROMBRINe). Brine is usually purified by a lime—soda treatment where the magnesium is precipitated with milk of lime (Ca(OH)2) and the calcium precipitated with soda ash. After separation from the precipitated impurities, the brine is sent to the ammonia absorbers. 

T. C. Ho and co-workers, "Metal Capture During Fluidized Bed Incineration of Wastes Contaminated with Lead Chloride," presented at the... 

Hydrogen Chloride as By-Product from Chemical Processes. Over 90% of the hydrogen chloride produced in the United States is a by-product from various chemical processes. The cmde HCl generated in these processes is generally contaminated with impurities such as unreacted chlorine, organics, chlorinated organics, and entrained catalyst particles. A wide variety of techniques are employed to treat these HCl streams to obtain either anhydrous HCl or hydrochloric acid. Some of the processes in which HCl is produced as a by-product are the manufacture of chlorofluorohydrocarbons, manufacture of aUphatic and aromatic hydrocarbons, production of high surface area siUca (qv), and the manufacture of phosphoric acid [7664-38-2] and esters of phosphoric acid (see Phosphoric acid and phosphates). 

Silver reduces the oxygen evolution potential at the anode, which reduces the rate of corrosion and decreases lead contamination of the cathode. Lead—antimony—silver alloy anodes are used for the production of thin copper foil for use in electronics. Lead—silver (2 wt %), lead—silver (1 wt %)—tin (1 wt %), and lead—antimony (6 wt %)—silver (1—2 wt %) alloys ate used as anodes in cathodic protection of steel pipes and stmctures in fresh, brackish, or seawater. The lead dioxide layer is not only conductive, but also resists decomposition in chloride environments. Silver-free alloys rapidly become passivated and scale badly in seawater. Silver is also added to the positive grids of lead—acid batteries in small amounts (0.005—0.05 wt %) to reduce the rate of corrosion. 

The advent of a large international trade in methanol as a chemical feedstock has prompted additional purchase specifications, depending on the end user. Chlorides, which would be potential contaminants from seawater during ocean transport, are common downstream catalyst poisons likely to be excluded. Limitations on iron and sulfur can similarly be expected. Some users are sensitive to specific by-products for a variety of reasons. Eor example, alkaline compounds neutralize MTBE catalysts, and ethanol causes objectionable propionic acid formation in the carbonylation of methanol to acetic acid. Very high purity methanol is available from reagent vendors for small-scale electronic and pharmaceutical appHcations. 

Niobium Pent chloride. Niobium pentachloride can be prepared in a variety of ways but most easily by direct chlorination of niobium metal. The reaction takes place at 300—350°C. Chlorination of a niobium pentoxide—carbon mixture also yields the pentachloride however, generally the latter is contaminated with niobium oxide trichloride. The pentachloride is a lemon-yeUow crystalline soHd that melts to a red-orange Hquid and hydrolyzes readily to hydrochloric acid and niobic acid. It is soluble in concentrated hydrochloric and sulfuric acids, sulfur monochloride, and many organic solvents. 

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