As a general rule of thumb, cleaning performance on
typical oily soils is enhanced with an increase in pH. Some soils, for example hard water
deposits, are best removed with acids.
Products at the two extremes (less
than pH 1 or greater than pH 13) are extremely oppressive and corrosive. Examples include,
sulfuric and hydrochloric acid on the acid end, and caustic soda on the alkaline end. Use
solutions of phosphoric or sulfamic acid cleaners, typically in the pH range of slightly
less than 2, may be described as "safe" acids comparison to the stronger acids.
Of course, necessary safety precautions (eye and hand protection) as noted on the Material
Safety Data Sheet should always be followed.
As an illustration of their non-aggressive behavior
in comparison to stronger acids, products containing sulfamic or phosphoric acid were
found to result in no chemical attack on nylon carpets. On the other hand, a hydrochloric
or powder acid-based product would basically dissolve the fibers.
Other than the two pH extremes, the pH scale
becomes secondary to the inherent properties of the specific chemical in terms of
corrosiveness. As an example, the pH of carbonated cola soda (which contains phosphoric
acid) is in the 2.5 range. A concentrated (35%) hydrogen peroxide solution has a pH of
approximately 3.5. Carbonated cola soda may be slightly irritating to the eyes, causing no
permanent damage. However, a 35% hydrogen peroxide solution will cause chemical burns to
the skin or mucous membranes. Thus, it is not the pH factor alone that causes corrosion of
products to surfaces.
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