Q:How to reduce surface roughness by optimizing degreasing process?
A:Choose a mild and efficient degreasing agent
Problems with traditional processes: Strong alkaline degreasing agents (such as sodium hydroxide) may cause slight corrosion to the substrate, forming a microscopic rough surface.
Optimization solution: ◦ Use weak alkaline degreasing agents (such as sodium carbonate + surfactant) or neutral degreasing agents (such as emulsifiers) to reduce corrosion on the metal surface.
For highly oily workpieces, ultrasonic degreasing can be used to enhance the oil removal efficiency through cavitation effect and avoid surface scratches caused by mechanical scrubbing.
Effect: Degreasing is more uniform and thorough, avoiding uneven subsequent pickling due to oil residue, and indirectly reducing roughness.
Q:How can the pickling process be optimized to reduce roughness?
A:Use mixed acid or add corrosion inhibitor:
Hydrochloric acid + hydrofluoric acid (HF) mixed acid: HF can dissolve silicides, suitable for steel containing silicon oxide scale, and reduce local corrosion.
Add organic corrosion inhibitors (such as thiourea, hexamethylenetetramine): inhibit excessive dissolution of the acid on the substrate, make the corrosion uniform, and reduce the roughness by 30%~50%.
Switch to phosphoric acid or aminosulfonic acid:
Phosphoric acid has mild acidity and low corrosion rate. It can form a phosphate conversion film, which has a certain leveling effect on the subsequent galvanized layer.
Aminosulfonic acid is non-volatile and suitable for pickling at room temperature to reduce excessive surface etching.
Q:How to reduce surface damage?
A:1. Avoid or replace sandblasting/shot blasting
Only for severely rusted workpieces: If it must be used, use fine sand or dry ice blasting instead, and control the pressure at 0.2~0.4MPa to reduce the depth of the pits.
Chemical rust removal is preferred: For mild to moderate rust, use pickling or rust converters (such as tannic acid) instead of mechanical treatment.
2. Mechanical grinding and refinement
If grinding is required, use progressive sandpaper for grinding:
Coarse grinding: 120#~240# sandpaper to remove burrs and protrusions.
Fine grinding: 400#~800# sandpaper to refine the surface and reduce the roughness to Ra 1.6~3.2μm.
Q:How to choose activation solution?
A:Weak acid activation solution: such as 5%~10% hydrochloric acid or sulfuric acid solution, replaces traditional strong acid activation. Acid-free activation: Use fluoroboric acid solution or aminosulfonic acid solution, with pH controlled at 2~3 to reduce secondary corrosion to the surface.
Q:What are the core principles of pre-processing optimization?
A:1. Gentle treatment is preferred: avoid strong corrosion and strong mechanical impact processes, and use chemical dissolution instead of mechanical removal.
2. Uniformity control: ensure uniform surface treatment by optimizing solution composition, temperature, time and equipment (such as ultrasound, electrolytic cell).
3. Collaborative process design: combine degreasing → pickling (with corrosion inhibitor) → chemical polishing → multi-stage water washing → weak activation to form a low roughness pretreatment process.
4. Online detection: use a roughness meter to monitor the roughness after pretreatment in real time and adjust process parameters.