Solvent Cold Cleaning and Vapor Degreasing,Solvent Cold Cleaning and Vapor Degreasing,Solvent Cold Cleaning and Vapor DegreasingSOLVENT CLEANING is a surface preparation process that is especially adept at removing organic compounds such as
grease or oil from the surface of a metal. Most organic compounds are easily solubilized by organic solvent and removed
from the workpieces. In some cases, solvent cleaning before other surface preparations can extend the life of cleaning
operations and reduce costs. In other cases, solvent cleaning prepares workpieces for the next operation, such as
assembly, painting, inspection, further machining, or packaging. Before plating, solvent cleaning is usually followed by
an alkaline wash or another similar process that provides a hydrophilic surface. Solvent cleaning can also be used to
remove water from electroplated parts, a common procedure in the jewelry industry.
Solvent cleaning can be accomplished in room-temperature baths or by using vapor degreasing techniques. Roomtemperature
solvent cleaning is referred to as cold cleaning. Vapor degreasing is the process of cleaning parts by
condensing solvent vapors of a solvent on workpieces.
Parts may also be degreased by immersion in the hot solvent, as well as by exposure to the solvent vapor. Drying is
accomplished by evaporating the solvent from the parts as they are withdrawn from the hot solvent vapor. In cold
cleaning, parts are dried at room temperature or by the use of external heat, centrifuging, air blowing, or an absorptive
medium.
The use of many industrial solvents is being severely restricted because of health, safety, and environmental concerns.
These concerns are discussed to some degree in this article; additional information is available in the articles
"Environmental Regulation of Surface Engineering" and "Vapor Degreasing Alternatives" in this volume.
Cold Cleaning
Cold cleaning is a process for removing oil, grease, loose metal chips, and other contaminants from the surfaces of metal
parts. Common organic solvents such as petroleum distillate fractions, chlorinated hydrocarbons, chlorofluorocarbons,
hydrofluorocarbons, or blends of these classes of solvents are used. Cleaning is usually performed at, or slightly above,
room temperature. Parts are cleaned by being immersed and soaked in the solvent, with or without agitation. Parts that are
too large to be immersed are sprayed or wiped with the solvent. Ultrasonic agitation is sometimes used in conjunction
with solvent cleaning to loosen and remove soils, such as abrasive compounds, from deep recesses or other difficult-toreach
areas. This reduces the time required for solvent cleaning of complex shapes.
Cold cleaning is chosen when one or more special conditions exist: water will not remove the soils, water would promote
corrosion or rusting, or soil must be removed from temperature-sensitive parts. Equipment for cold cleaning can be as
simple as a small tank or a pail with a cover. Thus, cold cleaning is a convenient choice for temporary operations, operations where each machinist must be able to clean parts, or operations where capital intensive equipment cannot be
justified.
Solvents
Table 1 lists aliphatic petroleums, chlorinated hydrocarbons, chlorofluorocarbons, alcohols, and other solvents commonly
used in cold cleaning. Stoddard solvent, mineral spirits, and VM&P naphtha are widely used because of their low cost and
relatively high flash points. The chlorinated hydrocarbons and chlorofluorocarbons exhibit a wide range of solvency and
are nonflammable, but most are far more expensive than the aliphatic petroleums. Blends of solvents are offered to
provide improved solvency, reduce cost, reduce fire hazard, adjust evaporation rates, and so on. The alcohols are used
alone, or in conjunction with chlorocarbons or chlorofluorocarbons, for special cold cleaning applications such as
removing activated soldering fluxes. Acetone and other solvents having low flash points are used for special purposes
only, such as cleaning the components of precision.
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