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Fundamentals of Corrosion
The procedures described concentrate on the technique and not the plastic.
In some cases, certain techniques are recommended for specific polymers.
It must be noted that many of the surface preparation processes involve the
use of hazardous, corrosive, toxic, flammable, and/or poisonous chemicals. It
is essential that appropriate control procedures and safe handling methods
be employed to minimize risk in the work environment.
7.6.3.1 Solvent Cleaning
The easiest and most common procedure used to remove surface contamination is by means of solvent action, which removes surface contamination by
dissolving the unwanted substance. Organic solvents and water are used for
this purpose.
Organic solvents may be flammable or nonflammable. The most commonly
used are acetone, methyl ethyl ketone, toluol, 1,1,1,-trichloroethane, naphtha,
and, on occasion, Freon (either by itself or blended with another solvent).
Although water is inexpensive and plentiful, it often has trace levels of
impurities that can contaminate surfaces. Consequently, distilled or deionized water is recommended. Water is frequently used as a rinse for other
surface preparation procedures.
These solvents can be applied in one of several methods, including simple wiping with a dampened cloth, immersion in a swirling bath with heat
applied to speed the solvent action, and spray cleaning. Spray cleaning has
the advantage of flushing off the contamination with the force of the spray.
Vapor degreasing is also employed. In this case, the plastic part is suspended over a boiling tank of solvent. As the vapors condense on the part,
the constant flow over the surface washes it clean. High-frequency vibration
from sonic waves in a solvent bath is also used to remove contaminants.
Before use, the compatibility of the solvent with the plastic must be verified. Regardless of the process used, frequent changing or filtering of the solvent is recommended to prevent buildup and recontamination. When using
heat to dry the parts after washing, care must be taken because heat can very
easily distort plastics.
7.6.3.2 Detergent Cleaning
Emulsification of oils, greases, and some mold releases is easily achieved
in either hot- or cold-water solutions of detergents or soaps. Recommended
materials include Ivory soap, Ajax cleanser, Borax (sodium borate), and trisodium phosphate (TSP) in various cleaning operations.
Unless the plastic is water sensitive, an immersion wash is effective.
Scouring with a medium-to-stiff brush works quite well for dislodging
many contaminants.
Because soap can act as a contaminant, it is essential that a thorough rinse
be applied using clean water. Thorough drying at elevated temperatures is
Fundamentals of Corrosion
The procedures described concentrate on the technique and not the plastic.
In some cases, certain techniques are recommended for specific polymers.
It must be noted that many of the surface preparation processes involve the
use of hazardous, corrosive, toxic, flammable, and/or poisonous chemicals. It
is essential that appropriate control procedures and safe handling methods
be employed to minimize risk in the work environment.
7.6.3.1 Solvent Cleaning
The easiest and most common procedure used to remove surface contamination is by means of solvent action, which removes surface contamination by
dissolving the unwanted substance. Organic solvents and water are used for
this purpose.
Organic solvents may be flammable or nonflammable. The most commonly
used are acetone, methyl ethyl ketone, toluol, 1,1,1,-trichloroethane, naphtha,
and, on occasion, Freon (either by itself or blended with another solvent).
Although water is inexpensive and plentiful, it often has trace levels of
impurities that can contaminate surfaces. Consequently, distilled or deionized water is recommended. Water is frequently used as a rinse for other
surface preparation procedures.
These solvents can be applied in one of several methods, including simple wiping with a dampened cloth, immersion in a swirling bath with heat
applied to speed the solvent action, and spray cleaning. Spray cleaning has
the advantage of flushing off the contamination with the force of the spray.
Vapor degreasing is also employed. In this case, the plastic part is suspended over a boiling tank of solvent. As the vapors condense on the part,
the constant flow over the surface washes it clean. High-frequency vibration
from sonic waves in a solvent bath is also used to remove contaminants.
Before use, the compatibility of the solvent with the plastic must be verified. Regardless of the process used, frequent changing or filtering of the solvent is recommended to prevent buildup and recontamination. When using
heat to dry the parts after washing, care must be taken because heat can very
easily distort plastics.
7.6.3.2 Detergent Cleaning
Emulsification of oils, greases, and some mold releases is easily achieved
in either hot- or cold-water solutions of detergents or soaps. Recommended
materials include Ivory soap, Ajax cleanser, Borax (sodium borate), and trisodium phosphate (TSP) in various cleaning operations.
Unless the plastic is water sensitive, an immersion wash is effective.
Scouring with a medium-to-stiff brush works quite well for dislodging
many contaminants.
Because soap can act as a contaminant, it is essential that a thorough rinse
be applied using clean water. Thorough drying at elevated temperatures is