Corrosion effect of solvents

The corrosiveness of perchloroethylene to copper is determined using Soxhlet apparatus. Three pre-weighed strips of copper are used, one placed in the bottom flask, the second in the bottom of the Soxhlet attachment, and the third below the condenser. The specimens are exposed to refluxing solvent for 72 h after which the entire apparatus is flushed with distilled water to wash all acidic substances back to the flask. The water layer is titrated with 0.01 N NaOH to determine its acidity and the strips are weighed to determine weight loss. The results indicate quahty of solvent. A different method is used to test copper corrosion by aromatic hydrocarbons. Here, a copper strip is immersed in a flask containing solvent and the flask is placed in boiling water for 30 min. Next, the copper strip is compared with ASTM standard corroded copper strips. 

1-trichloroethane is not properly stabilized it forms hydrochloric acid in the presence of aluminum. HCl corrodes aluminum. The presence of fi ee water invalidates the result of this test. An aluminum coupon is scratched beneath the surface of a solvent. The coupon is observed for 10 min and 1 h and the degree of corrosion is recorded in form of pass (no reaction) or fail (gas bubbles, color formation, or metal corrosion). The test is important to cleaning operations because alumimun should not be used for parts of machines (pumps, tanks, valves, spray equipment) in contact with corrosive solvent. 

The standard method for determining the specific gravity of halogenated organic solvents involves the use of both a pycnometer and a hydrometer as described above but, in addition, an electronic densitometer is also used. Here, a hquid is placed in U-shaped tube and subjected to electronic excitations. The density changes the mass of tube and fi equency of oscillations which is the basis for measurement and display of specific gravity readings. 

Two standard tables (American and metric system of units) are used to calculate weight and volume of benzene, toluene, xylenes mixture and isomers, styrene, cumene, and ethylbenzene as well as aromatic hydrocarbons and cyclohexane. Tables provide volume corrections for these solvents in a temperature range from -5 to 109 F (-20.5 to 43 C). 

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With the set-up it is possible to study the effect of solvent additives (eg foaming control, corrosion/degradation inhibitors). Therefore, the design of the pilot is such that differeut, uou-crystallising, solvent mixtures and modified types, both state-of-the-art chemical solvents and high load and activated solvents, can be tested. 

Surface Fluorination of Polymers. Fluorocarbon-coated objects have many practical appHcations because the chemically adherent surface provides increased thermal stabiHty, resistance to oxidation and corrosive chemicals and solvents, decreased coefficient of friction and thus decreased wear, and decreased permeabiHty to gas flow. Unusual surface effects can be obtained by fluorinating the polymer surfaces only partially (74). 

Ethylene oxide (qv), propylene oxide (qv), butylene oxide, and other epoxides react with ethanol to give a variety of Uquid, viscous, semiwax, and soUd products. These products are used ia the coatings iadustry as solvents, and as paints, antioxidants, corrosion inhibitors, and special-purpose polymers. Recent concerns about the health effects of ethanol containing glycol ethers have led to the decline in the production of these compounds. 

Less information is available about the stability of ceramic membranes. It is generally thought that ceramic membranes have excellent solvent stability. Acid conditions may be more problematic it was shown [57] that an alumina nanofiltra-tion membrane was very sensitive to corrosion effects in dynamic experiments, whereas the performance of a similar titania membrane was stable in the pH range from 1.5 to 13. 

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