Cleaning Compounds 153
they break soil down into smaller pieces and aid in its removal by destroying its attach- ment sites. They are classified as proteases because they break down protein and work best on the alkaline side at 60ºC or lower. These cleaners offer potential because they contain no chlorine or phosphates and are less corrosive than chlorine sanitizers. They can lower the pH of effluent. The disadvan- tages of enzyme-based cleaners are that liq- uid detergents require injection equipment and a two-part system activation, and they are not as effective on other soils as are chlo- rine sanitizers.
Phosphate Substitutes
for Laundry Detergents
Phosphates in laundry detergents have been prohibited in certain areas of the United States. Some of the substitutes for phosphates approved for use, such as car- bonates and citrates, have provided less acceptable results. Unbuilt liquids and phos- phate-built powders are more effective in soil removal and whiteness retention than are the carbonate-built powders. Carbonate-built detergents, although less expensive, tend to give less acceptable results because of deposit buildup on washed materials and on parts of the washer, especially with hard water.
Solvent Cleaners
Solvent cleaners are normally used on petroleum-based soils and greases in the maintenance area. Their use should be strictly controlled. Solvent cleaners are ether- or alco- hol-type materials capable of dissolving soil deposits. These compounds are most fre- quently used to clean soils caused by petro- leum products, such as lubricating oils and greases. These cleaners may contain a foaming agent to aid in the application and cleaning. Unlike alkaline cleaners that digest organic materials, solvents “melt” or break down these compounds. Because most organic soils are
saponified through alkaline cleaners, an alka- line or a neutral cleaning compound is more frequently used. However, solvent cleaners are frequently used if large amounts of petroleum deposits exist. A solvent-type cleaner is fre- quently required to remove this type of soil deposit from equipment. This type of soil will not usually be found directly on processing equipment surfaces, but rather in the general area.
Solvent cleaners are derived from various volatile materials from the petroleum indus- try and combined with wetting agents, water softeners, and other additives. Heavy-duty solvent cleaners are immiscible with water and frequently form an emulsion when water is added. Heavy-duty solvent cleaners are manufactured for use without water, whereas some solvent cleaners with low solvent con- tent can be combined with water and still exhibit the grease-cutting action expected from a solvent.
Detergent Auxiliaries
Detergent auxiliaries are additives included in cleaning compounds to protect sensitive surfaces or to improve the cleaning properties of the compound.
Protection Auxiliaries
Acid Compounds
Acids may be used with synthetic cleaning compounds for cleaning alkaline-sensitive surfaces-for example, surfaces coated with alkaline-sensitive paints or varnishes, and light metal cleaning. The following acids are useful in protecting sensitive surfaces:
● Phosphoric acid is used to clean metals before painting, because it removes rusts and metal scales, and subsequently pas- sivates the surface.
● Oxalic acid, which effectively removes iron oxide rust without attacking the metal, although precautionary steps are
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