The effectiveness of the cleaning agents, the quality, the costs and the level of stability of a washing cycle of metal parts depend mainly on the ability of the detergent used to remove contaminants.
In general, a cleaning agent must be able to:
- Remove and eliminate the contaminants present on the parts to be treated
- Dissolve, dilute, emulsify and wash away the substances that have physically accumulated on the surface of the parts
What are the key factors influencing the choice of cleaning agents?
The choice of a cleaning fluid must be made taking into account a series of factors, namely:
- TYPE OF CONTAMINATION: oil, grease, wax, emulsions, polishing or lapping pastes, various fragments, dust, enamel, flammable agents, etc .;
- MATERIAL TO CLEAN: steel, cast iron, non-ferrous metals, alloys, aluminum, glass, plastic, ceramics, etc .;
- GEOMETRY OF THE COMPONENTS: holes, cuts, threads, porous surfaces etc .;
- Final CLEANLINESS REQUIREMENTS for metal parts;
- TEMPERATURE and DURATION of the treatment, technology adopted by the machine and by the process;
- SCOPE and QUALITY of the necessary maintenance measures.
In most cases, the most commonly used cleaning agents are water-based ones and solvents that fall into one of the following categories:
- HC: non-halogenated hydrocarbons;
- CHC: chlorinated or halogenated hydrocarbons;
- Modified alcohols.
The “like dissolves like” chemical principle is a good rule when choosing a good cleaning agent.
In chemistry, the “like dissolves like” rule refers to solubility and polar and non-polar substances.
In practice, the rule says that most typically, polar solutes can dissolve in polar solvents and non-polar solutes can dissolve in non-polar solvents.
Non-polar contaminants include grease, resins, wax and processing oils which are usually removed with non-polar solvents such as non-halogenated hydrocarbons, chlorinated hydrocarbons and partly modified alcohols.
Residues and particles are no longer able to adhere to the surface when the oil is removed by mechanical processes such as spray or ultrasonic washing and injection immersion washing.
Characteristics and properties of the main cleaning agents
The best way to choose the cleaning agent that suits your needs is to try to know their characteristics and specifications: let’s see together.
Solvents have different and specific chemical properties that make them usable in a number of numerous applications.
In general, solvents are characterized by a high compatibility rate and when used for parts cleaning they do not cause oxidation, discoloration or other undesirable effects on the surface of the components.
Furthermore, the solvents allow you to achieve successfull cleaning results even with geometrically challanging parts.
For the systems that use water-based cleaning agents, the controls of agent concentration level, contamination, pH value and conductance are not needed.
HC, NON-HALOGENATED HYDROCARBONS
These cleaning agents are ideal for eliminating animal, vegetable, mineral oil and various fats; they are also used to degrease metals and remove oils and greases used in modern production processes.
CHC, CHLORINATED HYDROCARBONS
This category includes substances such as Perchlorethylene which provide excellent results and have sufficient ability to remove grease where low surface tension and high chemical stability are present.
This type of cleaning agents are also suitable for degreasing and cleaning components with complex geometry.
Please read more on the use of Perchlorethylene in complete safety.
Modified alcohols are also known as polar solvents and are capable of removing both non-polar fats and oils as well as polar contaminants.
Before choosing a cleaning agent, it is good to evaluate the compatibility with the material and perform a series of tests to determine what are the results that could be achieved.
Other types of cleaning agents
In addition to the categories mentioned above, there are other series of agents: water-based, acid and alkaline agents.
Aqueous detergents can be in liquid or powder form with acidic, neutral or alkaline formulation. Aqueous cleaners are usually used for polar contaminations such as salts, refrigerant emulsions and water-based and solid lubricants such as dust, chips and rubs.
The structure of these agents always includes surfactant detergents and a base that work in complete synergy.
The acidic and mildly acidic cleaning agents contain phosphoric, sulfuric, citric or hydrochloric acids and are used in the presence of inorganic contaminations such as powders, pigments, rust, encrustations and discolorations to deoxidate after deburring operations and to activate before the application of particular coating.
Alkaline agents have a PH between 10 and 14, contain alkaline hydroxide (silicates, phosphates) and are suitable for removing the toughest contaminants such as heavy oils, lapping compounds and polishes.
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