1.What are the principles and methods of alkaline degreasing and cleaning?
Principle: Utilizing the saponification and emulsification effects of alkaline cleaning agents (typically containing sodium hydroxide, sodium carbonate, silicates, surfactants, etc.) to decompose and peel off mineral oils and animal/vegetable oils.
Methods:
Spray Cleaning: Performed through a high-pressure spray system; highly efficient and suitable for continuous production lines.
Immersion Cleaning: Steel coils are immersed in a cleaning tank; suitable for thicker oil stains.
Advantages: Relatively low cost, mature technology, good cleaning effect, suitable for large-scale processing.
Disadvantages: Requires a wastewater treatment system; high energy consumption (usually requires heating).
Post-Cleanup: Must be thoroughly rinsed with clean water (preferably deionized water) and dried immediately; otherwise, water rust is highly likely to form.
2.What are the principles and methods of solvent cleaning?
Principle: Uses organic solvents (such as hydrocarbon solvents, halogenated hydrocarbons, etc.) to directly dissolve oil stains.
Methods: Immersion, steam degreasing, or ultrasonic cleaning.
Advantages: Fast cleaning speed, good volatility, no rinsing required, quick drying, and strong dissolving power for complex oil stains.
Disadvantages: High cost, most solvents are flammable, explosive, or toxic, requiring strict explosion-proof and ventilation measures, and significant environmental pressure. Currently, there is a greater preference for using environmentally friendly solvents.
3.What are the principles, advantages, and disadvantages of emulsification cleaning?
Principle: This method uses an emulsified cleaning agent, which dissolves some oil and forms an emulsion with water, facilitating rinsing.
Advantages: It combines the cleaning power of solvents with the safety of water-based cleaning agents, offering stronger cleaning power than soda ash.
Disadvantages: Waste liquid treatment is more complex than that of alkaline wastewater.
4.What are some auxiliary or small-scale/on-site treatment methods?
Manual Cleaning
Tools: Cloth, brush, roller, etc.
Cleaning Agents: Special metal cleaners, solvents (such as acetone, alcohol, or specialized cleaners), or diluted alkaline cleaning solutions can be used.
Suitable Scenarios: Small area, spot cleaning, repairs, or small-scale work.
Caution: Protective equipment must be worn, and ventilation must be ensured. Solvents such as acetone have strong degreasing capabilities but are flammable and harmful to humans.
Special Industrial Wiping Paper/Cloth
Principle: Special non-woven fabric pre-impregnated with cleaning solvent.
Advantages: Convenient and quick, disposable, leaves no residue, especially suitable for final cleaning before welding and bonding.
Disadvantages: High cost, only suitable for cleaning small areas or critical parts.
5.What are the selection methods and key considerations?
Clearly define subsequent process requirements:
Welding/Spraying: Absolutely no residue is required; otherwise, it will lead to incomplete welds, porosity, or coating peeling. A complete process of "degreasing → rinsing → drying" is typically required, followed by inspection with a white cloth.
Ordinary forming processing: Requirements can be appropriately reduced; only most oil stains need to be removed to ensure cleanliness of operation and molds.
Assess the state of oil stains:
Light rust-preventive oils and heavy rolling oils or contaminated greases present different cleaning difficulties.
Drying is essential:
Immediate and thorough drying after using any water-based cleaning agent is the most critical step in preventing cold-rolled coils from rusting. Drying temperatures should not be too high to avoid affecting material properties or causing oxidation discoloration.
Environmental protection and safety:
Prioritize environmentally friendly water-based cleaning agents and equip the system with a wastewater treatment system.
When using solvents, strictly adhere to fire prevention, explosion prevention, ventilation, and occupational health regulations.