Cleaners are categorized according to chemical type and application. There are 5 primary types of cleaners of interest:
Solvent cleaners are straight petroleum distillates which can come with a variety of flash points, viscosities, rendered film types and odors. When selecting a solvent cleaner, care must be taken with regard to nearby sources of ignition, application (i.e., spray, dip or wipe), residual film requirements, and VOC.
Emulsion cleaners are emulsifiable petroleum-based mixtures which may also contain surfactants for added detergency. Emulsion cleaners typically leave an oily film for rust protection and are good at removing petroleum-type soils, and buffing or polishing compounds.
Detergent cleaners are cleaners that are principally composed of surfactants and work by the emulsification of soils. Benefits derived from using a detergent cleaner are their low alkalinity, safety in handling, good residual rust protection and the fact that many do not contain chelating agents. A wider variety of metals can be cleaned by detergents due to their low alkalinity, while a drawback to some detergents is their tendencies to produce foam.
Alkaline cleaners are generally sodium or potassium hydroxide-based cleaners that also contain detergents (for wetting), builders, and other additives. Alkaline cleaners are best on fatty soils as the hydroxides saponify the fat and create soap. Drawbacks include potential safety hazards, and they are not as versatile as detergent-types, as they could tarnish aluminum and yellow metals.
Acidic cleaners can be composed of organic or inorganic acids and can be used in ultrasonic, dip and vibratory cleaning operations. Acidic cleaners are used to brighten and clean metals and are particularly useful on hard water soils. Care must be taken when recommending an acid with regard to materials of construction and waste disposal.