In current industrial production, stainless steel polishing processes are mainly divided into four categories: mechanical polishing, chemical polishing, electrolytic polishing, and fluid polishing. The principles and operational characteristics of each process differ significantly, requiring precise selection based on product structure, material grade, and application requirements. In some scenarios, a “composite process” (such as mechanical rough polishing + electrolytic fine polishing) is employed to improve efficiency and effectiveness.
Mechanical Polishing: The principle of mechanical polishing involves using tools such as grinding wheels, fiber wheels, and wool wheels in conjunction with abrasives to physically cut the stainless steel surface. Defects are gradually removed and surface roughness reduced through rough polishing, medium polishing, and fine polishing. Key operational points: Rough polishing uses an 80-120 grit grinding wheel to remove machining marks; medium polishing uses a 400-800 grit fiber wheel to refine the surface; and fine polishing uses diamond polishing paste in conjunction with a wool wheel to achieve a high gloss finish. Throughout the process, speed and pressure must be controlled to avoid localized overheating that could lead to metal deformation. Advantages and limitations: Low cost, high controllability, suitable for all stainless steel grades; however, it has low polishing efficiency for complex structures (such as internal holes, threads, and tee heads) and is prone to human error. **Applicable Scenarios:** Flat and simple curved stainless steel products, such as stainless steel plates, valve flanges, general pipe fittings, and building panels.
**Chemical Polishing:**
**Principle:** Utilizing the selective dissolution property of a nitric acid-hydrofluoric acid mixture, it preferentially corrodes the microscopic protrusions on the stainless steel surface, making the surface smoother. No electricity or complex equipment is required.
**Operating Points:** Strictly control the polishing solution ratio (add 5-10% glycerin to prevent excessive corrosion) and temperature (60-80℃). Rinse immediately with deionized water after polishing and neutralize residual acid with sodium bicarbonate solution.
**Advantages and Limitations:** Can process multiple workpieces simultaneously, high efficiency, low cost, suitable for thin-walled parts and complex structures; however, waste polishing solution treatment is costly, and it is difficult to control the surface uniformity of complex parts.
**Applicable Scenarios:** Large-volume production of small, complex parts, such as stainless steel fasteners, precision small pipe fittings, and kitchen hardware accessories.
**Chemical Polishing:** Electrolytic Polishing
Principle: Using stainless steel as the anode, an electric current is passed through a phosphoric acid-sulfuric acid electrolyte. Utilizing the principle of “electrochemical anodic dissolution,” the current density on surface protrusions is increased, leading to faster dissolution and microscopic leveling, while simultaneously forming a dense passivation layer. Key Operating Points: Control the electrolyte temperature to 55-60℃, current density to 15-50 A/dm², and polishing time to 5-10 minutes. Subsequent nitric acid passivation treatment is required to further enhance corrosion resistance. Advantages and Limitations: High polishing precision, with surface roughness reaching below Ra0.05μm, and superior corrosion resistance compared to mechanical polishing; however, high equipment investment and professional operation are required, otherwise over-corrosion and color differences may occur. Applicable Scenarios: Products with stringent requirements for corrosion resistance and surface finish, such as medical devices, food machinery, vacuum equipment, and precision chemical pipelines.
Fluid Polishing
Principle: Utilizing a high-pressure pump to deliver an abrasive fluid (silicon carbide powder + polymer medium), microscopic cutting is achieved by flowing across the workpiece surface. This is a “flexible polishing” technology. Key Operating Points: Select the abrasive grit size according to the workpiece’s hole diameter and structure, and control the pumping pressure and flow rate. The abrasive can be recycled. Advantages and Limitations: It can overcome dead angles that traditional processes cannot reach, such as internal holes, intersecting holes, and blind holes; however, processing time for a single workpiece is relatively long, making it suitable for small batches of precision parts. Applicable Scenarios: Polishing of complex structural parts such as stainless steel tees, precision internal pipe fittings, and hydraulic valve sleeves.
Furthermore, stainless steel polishing results in different surface grades, such as 2D (matte), 2B (smooth matte, most commonly used), BA (high gloss), No.4 (uniform reflective), HL (brushed), and No.8 (mirror). Different grades correspond to different polishing process combinations and are important indicators of product specifications in industrial production.
Post time: Jan-22-2026