The problem of uneven surface gloss (yin and yang) on ​​bright stainless steel pipes is primarily related to the polishing process, material handling, and environmental factors.
The following are targeted solutions and precautions:
1. Mechanical Polishing Correction
Rough Polishing: Use 400-1500 grit sandpaper or a belt sander to remove surface scratches and oxide layers, focusing on dark areas.
Fine Polishing Optimization: Use a wool wheel with 0.25-1 micron diamond paste to repeatedly polish the interface between the yin and yang surfaces until the finish reaches Ra < 0.01 micron.
2. Electrochemical Polishing Adjustment
Current Density Control: Reduce the anodic current density to 10-30 A/dm² to prevent excessive corrosion on sharp corners.
Electrolyte Maintenance: Regularly check the concentration of the phosphoric acid-sulfuric acid mixture to prevent grayish discoloration caused by failure.
3. Auxiliary Pickling and Passivation
Weld Seam Treatment: First, pickle the weld area with a nitric acid-hydrofluoric acid mixture, then passivate to form a uniform oxide film and reduce color variation. Post-chemical polishing: Neutralize residual acid with 5% sodium hydroxide to prevent secondary oxidation.
4. Environment and Operating Specifications
Dust-free operation: Polishing must be performed in a clean room to avoid dust adhesion and localized matte finish.
Shielding device application: Install cathode shields on sharp corners to balance current distribution.
If scratches exist on the surface, fill them with plaster first, then use a brushing process (straight or circular) to transition between the positive and negative surfaces. For high-quality mirror finish tubes, chemical mechanical polishing (CMP) is recommended to improve consistency.