I. Chemical Treatments
1. Pickling and Passivation: Pickling removes surface oxide scale and weld spots, forming a dense passivation film. This is the default process for industrial stainless steel pipes, resulting in a matte silver-white finish with strong corrosion resistance.
2. Bright Annealing: Annealing is performed under vacuum or a protective atmosphere to eliminate cold working stress, resulting in a bright and clean surface with Ra≤0.4μm. This is often used for high-purity gases and sanitary pipelines.
3. Chemical Polishing: Immersion in a special acid solution achieves overall brightness. This method can handle complex-shaped pipes and is less expensive than electrolytic polishing.
II. Mechanical Treatments
1. Mechanical Polishing: Using abrasive belts and polishing wheels, this process involves rough, medium, and fine polishing to achieve mirror (8K), brushed, and matte effects. The surface finish is approximately Ra 0.4-0.8μm, and it is easy to clean and maintain. 2. Sandblasting/Shot peening: Surface blasting with quartz sand, alumina, etc., creates a rough, matte finish. Shot peening with spherical shot can simultaneously strengthen the surface and improve the pipe's fatigue resistance.
3. Brushing/Oil polishing: Creates directional textures with a subtle matte finish, concealing minor scratches. This is a common process for decorative stainless steel pipes.
III. Electrochemical Treatments
Electrolytic polishing: Anodicly dissolves microscopic protrusions on the surface, resulting in an ultra-smooth surface (Ra≤0.1-0.2μm), significantly improving corrosion resistance. It is widely used in high-cleanliness environments such as medical, pharmaceutical, and high-purity fluid applications.
IV. Special/Coating Treatments
Plastic coating/plating: Applying PE/EP plastic or electroplating chromium/nickel achieves corrosion resistance, coloring, and wear resistance, suitable for applications with special protection requirements.
