The first method is emulsification, which uses the amphiphilicity of surfactant to adsorb oil molecules at the lipophilic end and water molecules at the hydrophilic end, and forms a suspension emulsion through rolling emulsification, thus washing off the oil stains on the surface of the cleaned workpiece.
The second method is solvent method, in which oil is insoluble in water but soluble in organic solvent, so that the oil stain is dissolved and dispersed in the solvent, and the oil stain and the cleaned workpiece are stripped and removed.
The third method is saponification, in which esters (especially carboxylic esters) are hydrolyzed under the action of alkali to produce carboxylic esters and alcohols, and then the organic matter to be extracted is obtained. Like surfactant cleaning oil stains, the oil stains on the surface of the workpiece can also be stripped and cleaned.
However, in the face of increasingly strong regulatory pressure, the use of traditional solvents and strong bases has decreased.
Therefore, the use of water-based or non-volatile solvent cleaning agents and degreasing agents is increasing. Judging from the cleaning effect, the water-based metal cleaning agent technology is close to maturity. In industrial application, the three principles of removing oil stains can be divided into the following two kinds of cleaning agents, namely solvent-based cleaning agents and water-based cleaning agents.