require alkaline cleaners with a pH of 11 or
higher.
Strongly Alkaline Cleaners
These cleaners have strong dissolving
powers and are very corrosive. They can
burn, ulcerate, and scar skin. Prolonged con-
tact may permanently damage tissue. Inhala-
tion of the fumes or mist may cause
respiratory tract damage. Mixing strong
alkaline cleaners with water causes an
exothermic reaction; the heat generated may
cause the solution to boil or vaporize. Such
explosive boiling may spray caustic com-
pound on the bystanders.
Examples of strongly alkaline compounds
are sodium hydroxide (caustic soda) and
silicates having high N 2 O:SiO 2 ratios. The
addition of silicates tends to reduce the cor-
rosiveness and improves the penetrating and
rinsing properties of sodium hydroxide.
These cleaners are used to remove heavy
soils, such as those from commercial ovens
and smokehouses, and have little effect on
mineral deposits. Caustic soda, which has
highly germicidal activity, protein dissolu-
tion, and deflocculation/emulsifying proper-
ties, is used for removing heavy soils. Because
of its potential damage to humans and
equipment, caustic soda is not used as a
manual cleaner.
Heavy-Duty Alkaline Cleaners
These compounds have moderate dissolv-
ing powers and are generally slightly corro-
sive or noncorrosive. Prolonged contact with
body parts may remove necessary oils from
the skin, leaving it vulnerable to infections.
The active ingredients of these cleaners may
be sodium metasilicate (a good buffering
agent), sodium hexametaphosphate, sodium
pyrophosphate, sodium carbonate, and
trisodium phosphate, which are known for
its good soil-emulsification activity. The
addition of sulfites tends to reduce the
corrosion attack on tin and tinned metals.
These cleaners are frequently used with high-
pressure or other mechanized systems. They
are excellent for removing fats but have
no value for mineral deposit control. Sodium
carbonate, which is one of the oldest alkaline
cleaners, functions primarily as a buffering
agent. Borax may be added as a buffer-
ing agent. Sodium carbonate, which is rela-
tively low in cost, is used as a buffering agent
in many formulations and has a wide range
of uses in heavy-duty and manual cleaning
applications. Chelators and wetting agents
are normally added to tie up minerals and
enhance free rinsing respectively.Mild Alkaline Cleaners
Mild cleaners frequently exist in solution
and are used for hand cleaning of lightly
soiled areas. Examples of mild alkaline com-
pounds are sodium bicarbonate, sodium
sesquicarbonate, tetrasodium pyrophosphate,
phosphate water conditioners (sequesters),
and alkyl aryl sulfonates (surfactants). These
compounds have good water-softening capa-
bilities but exhibit no value for mineral
deposit control.
Table 9–5 summarizes cleaning character-
istics of commonly used alkaline cleaners.
Comparisons of emulsifying properties,
detergency, and corrosiveness are also pro-
vided.Chlorinated Alkaline Cleaners
Hypochlorite is added to these cleaners to
peptize the proteins for easier removal.
These cleaners are well adapted to cleaning-
in-place (CIP) of pipes, tanks, and vats and
remove effectively fats, oils, grease, and pro-
teins.Acid Cleaning Compounds
These compounds, especially blends of
acids such as phosphoric, nitric, sulfuric,
and sulfamic, remove encrusted surfaceCleaning Compounds 149