Aqueous - water based products that can come in four subgroups
Acidic - pH less than 7. Acidic cleaning is routinely used to remove scale, rust, and oxides from metals. The cleaners may contain mineral acids (hydrofluoric, sulfuric, phosphoric, nitric), chromic acids, or organic acids (acetic or oxalic). They also may contain detergents, chelating agents, and small amounts of water-miscible solvents.
Alkaline - pH greater than 7 and less then 12. They are the most common solutions in aqueous cleaning. Alkaline cleaners often contain additives to improve cleaning, such as sequestering agents, emulsifiers, and surfactants. Inhibitors are necessary with some metals, especially aluminum.
Caustic - ph greater than 12, usually cotian sodium hydroxide or potassium hyrdoxide.
Neutral - are mixtures of water and other chemical compounds with a pH near 7. The chemical compounds may include surfactants, corrosion inhibitors, and other additives. Neutral and alkaline aqueous solutions are the most commonly used aqueous solutions. They will work for most solvent substitution applications.
Semi-Aqueous - are semistable mixtures of water and solvents, also called emulsions. Semiaqueous cleaning also includes processes where parts are first cleaned in a solvent, then rinsed in water. The solvents are usually volatile organic compounds (VOCs) such as terpenes, glycol ethers, esters, or hydrocarbons. These solvents are also flammable when used by themselves, or pure. Most semiaqueous solutions leave a residue that can be removed with a water rinse. Sometimes the film is left on the part as a protective coating.
Terpene - are organic solvents that are usually derived from natural sources such as pine trees or citrus fruit. They generally have strong characteristic odors. Specific terpenes used in cleaning are a-pinene, d-limonene, and turpentine, which is a mixture of terpenes. Terpenes are volatile organic compounds (VOCs) and are flammable or combustible.
Petroleum distillates - are hydrocarbon solvents produced from crude oil. These solvents include mineral spirits, kerosene, white spirits, naphtha, and Stoddard solvent.
Alcohols - commonly used alcohols in cleaning include methanol, ethanol, and isopropanol (IPA). IPA is the most widely used. They are all volatile organic compounds (VOCs), with vapor pressures ranging from 33 to 92 mmHg at 68 deg F (44 to 122 mbar at 20 deg C). They are also flammable and must be handled accordingly.
Di-Basic Esters (DBE) - are a mixture of methyl esters of adipic, glutaric, and succinic acid. DBE is commonly used as a paint stripper.
Ethyl Lactate - Ethyl lactate (ethyl 2-hydroxypropionate) is a commercially available monobasic ester solvent.
Glycol Ether - are organic solvents. Many different glycol ethers are used for cleaning
Bio-based - is composed, in whole or in significant part, of biological products or renewable domestic agricultural materials (including plant, animal, and marine materials) or forestry materials.
Halogenated - sovlents that contain one or more of the Halogen chemicals (typically fluorine, chlorine or bromine).