Cleaning agents and surface treatments include liquid cleaners, degreasers, strippers, passivators, etchants, solutions, and additives for cleaning and surface preparation. They are used to clean contaminants such as grease or oil off of surfaces such as industrial equipment or mechanical components. They are also used to disinfect or sterilize equipment used in cleanrooms, laboratories, and similar applications.

Cleaning agents and surface treatments clean and prepare surfaces by interacting or reacting with contaminants and altering their properties. The removal methods are generally specific to each type; however the end result of each is the removal, loosening, or transformation of contaminants from the surface or material.

Types of Cleaning Agents and Surface Treatments

Cleaners consist of a large array of different chemicals and substances. They can be classified into different types based on their consistency and function.

• Strong alkali cleaners are extremely caustic solutions used to dissolve greases and protein deposits and to destroy microbes, making them fit for cleaning and sanitation purposes. Examples include sodium hydroxide and potassium hydroxide.
• Medium alkali cleaners are somewhat caustic solutions used to remove fats, oils, and some paints and lacquers. Sodium carbonate, also known as wash soda, is an example.
• Mild alkali cleaners are slightly basic solutions used for water softening and light cleaning. Sodium bicarbonate is an example.
• Strong acids are highly corrosive acids used to dissolve surface mineral deposits. Examples include sulfuric and hydrofluoric acids.
• Mild acids are slightly corrosive acids used to soften water and control mineral deposition. Examples include acetic and gluconic acid.
• Solvents include a variety of substances used to dissolve grease and oil without the hazards of corrosivity. Solvent cleaners consist of compounds such as alcohols, chlorinated hydrocarbons, or terpenes in solution (either added or as the base). Examples include acetone and d-limonene.
• Soaps and detergents are used to emulsify fats, oils, and greases and are widely used as household cleaners. Soaps are produced naturally by reactions between fatty acids and basic salts. Detergents are basic salts produced synthetically.

*Property varies with solvent type

Table 1 - Overview of cleaning agent types. Table Credit: Cole-Parmer

Other types of cleaning agents include contact cleaners and compressed gases such as aerosols and dusters used on electronics, etchants and pickling solutions used for aggressive passivation of metals, and bioremediation systems utilizing microorganisms to breakdown contaminants.

Product Performance

To ensure proper performance and process compatibility, a number of cleaner performance specifications should be considered. These include concentration, pH, form, and use temperature.

• Concentration is the ratio of cleaning agent abundance to total solution volume. It consequently measures the strength of the cleaning agent. A full strength cleaning product is undiluted and is distributed in its most concentrated form. Concentration must be considered with the purchase of any cleaning solution to ensure proper cleaning strength and consistency.
• pH, or potential of Hydrogen, is a measure of the acidity or alkalinity of the substance, ranging between 0 and 14. pH plays a role in the function and cleaning power of acid (low pH) or alkaline (high pH) solutions. However, solutions with very high or very low pH are also much more hazardous to both equipment and personnel.
• Form is the consistency of a cleaning agent. While most cleaning agents are liquids, some can be compressed gases, gels, pastes, semi-solids, powders, or pellets. Products that come in solid form are sometimes added to water or other solvents to make a solution. Form is important for correct application and implementation of the product into a system or process.
• Use temperature is the designed operating temperature of the cleaning product. Some solutions are designed to be used in hot conditions to help encourage molecular interaction in the cleaning process. The cleaning product must be designed to work effectively within the temperature range of its corresponding system.

Features

For specific applications, certain features of cleaning agents may be especially important. Cleaning products may be anti-static, non-toxic, VOC compliant, biodegradable, foam free/low foaming, non-corrosive, and/or non-flammable.

Applications

Cleaning agents and surface treatments are used in an endless number of applications. However, some common examples include the use of industrial cleaners for chemical and mechanical equipment, etchants and pickling solutions for metal surface preparation, and surfactants for emulsifying wastewater solids.

References

Cole-Parmer - Types of Cleaning Compounds, Table 1

DOW, Chemaware^TM - Solvents

Essential Industries, Inc. - The Chemistry of Cleaning

Image Credit: All-Spec Industries