Cleaning Targets: Workpieces typically require cleaning from materials such as aluminum, copper, iron, and zinc alloys. Consider the type of surface contaminants (oil, wax, dust, etc.) accumulated during production; the complexity of the workpiece structure (whether it has gaps or blind holes); whether the surface coating is easily scratched or peeled off; whether it is prone to rust; whether the workpiece is a composite material (e.g., alloy with embedded plastic); and any special requirements regarding chemicals (e.g., prohibited chemicals, environmental requirements, acidity/alkalinity).
Cleaning Conditions: Before starting cleaning, understand the object to be cleaned and the cleaning environment. Key points include:
1. Check for any residue on the surface of mechanical workpieces;
2. Assess the equipment's rust and discoloration prevention capabilities, and whether strong alkaline cleaning agents can be used;
3. Investigate any surface treatment processes such as electroplating, blackening, anodizing, painting, PVD coating, or vacuum coating.
Cleaning Agent Selection: Due to the different substrates being cleaned, selecting the appropriate cleaning agent is crucial. Cleaning environments are categorized as neutral, acidic, or alkaline. Correctly selecting surfactants plays a vital role in this process.
1. To improve the pickling effect during pickling—namely, accelerating the dissolution of the oxide layer, delaying acid corrosion of the substrate, and inhibiting the diffusion of hydrogen atoms into the substrate—a small amount of surfactant is often added to the metal pickling solution. This is because the added surfactant forms a thin film on the metal surface, providing a certain degree of corrosion inhibition.
2. In alkaline washing, the main role of surfactants is to reduce surface tension, emulsify, and disperse dirt, thereby significantly improving cleaning efficiency. Nonionic surfactants (such as alkylphenol polyoxyethylene ethers, polyethers, etc.) have good wetting and penetrating abilities. ① Adding a small amount of surfactant can reduce the surface tension between the substrate and the liquid surface, and improve penetration, allowing the alkaline solution to better contact the oil stains, forming a saponification reaction and removing some of the grease.
② Adding surfactants can increase the emulsification and dispersion of grease.
③ In the solvent cleaning process, the main surfactants used are ethylene oxide adducts of esters, ethers, and amines, or mixtures thereof. Compounds of nonionic and anionic surfactants can also be used.
The choice of surfactant depends on the type of solvent and the type of cleaning emulsion to be prepared. In addition, certain co-solvents should be added to solvent-based cleaning agents to increase the solvent's solubility (such as higher alcohols, ethylene glycol, ethylene glycol derivatives, etc.).