What are the surface treatment processes for stainless steel decorative pipes and water pipes

The surface treatment processes for stainless steel decorative pipes and water pipes vary significantly due to different functional requirements. Decorative pipes focus more on aesthetics, while water pipes emphasize hygiene and corrosion resistance. Here are the common surface treatment processes and characteristics of both: 

I. Surface Treatment Process of Stainless Steel Decorative Pipes

1. Polishing Processes (Enhancing Glossiness and Decorativeness)

Mirror Polishing (8K/10K Polishing)

Process: Through multiple grinding and polishing with abrasives (such as aluminum oxide, chromium oxide), the surface roughness Ra is ≤ 0.2 μm, creating a mirror-like reflective effect.

Characteristics: The surface is as shiny as a mirror, providing a luxurious visual effect, commonly used in high-end decorations (such as hotel facades, elevator carriages), but prone to leaving fingerprints and scratches.

Sand Blasting (Sanding / Matte Polishing)

Process: Uniformly sanding the surface with sandpaper, sand belts, or sandblasting (quartz sand, glass beads) to form a matte texture.

Characteristics: The surface is non-glossy but has a fine texture, with better scratch resistance than the mirror surface, commonly used in stair handrails, guardrails, etc., where contact is frequent.

Brushing (Hairline Texture Treatment)

Process: Using a brush or steel wire wheel on the surface to create parallel fine lines (straight lines, random lines), forming a texture similar to metal hair.

Characteristics: The texture is clear, highly decorative, and can cover minor scratches, commonly found on furniture, advertising board frames.

2. Color and Coating Processes (Enriching Appearance Effects)

Titanium Plating (PVD Vacuum Coating)

Process: In a vacuum environment, through physical vapor deposition (PVD), titanium, zirconium, etc. metal ions are attached to the surface to form colored oxide films (such as gold, rose gold, black).

Characteristics: The color is long-lasting and does not fade, resistant to wear, and enhances corrosion resistance, suitable for outdoor decorations (such as landscape sculptures).

Electrophoretic Coating

Process: The pipe is immersed in water-soluble coatings and then electrically charged to evenly attach the coatings, followed by high-temperature curing to form a protective film.

Characteristics: The coating thickness is uniform (10~30 μm), has bright colors, strong resistance to ultraviolet rays and oxidation, commonly used in stainless steel decorative parts for aluminum alloy windows and doors.

Spraying (Powder Spraying / Fluorocarbon Spraying)

Process: Powder spraying is to attach plastic powder through electrostatic adsorption on the surface and then heat cure to form a protective film; fluorocarbon spraying uses fluorocarbon coatings (such as PVDF) for spraying and then drying.

Characteristics: Powder spraying has rich colors and low cost, fluorocarbon spraying has extremely strong weather resistance (suitable for coastal or acid rain environments), commonly used in outdoor guardrails.

3. Texture and Texture Processes (Personalized Design)

Stamping (Rolling Pattern)

Process: Through rolling rollers on the surface to press out patterns (such as rhombus, waves, tree bark patterns), creating a three-dimensional tactile sensation.

Characteristics: It adds decorative layering, commonly used in handrails, screens, etc., where tactile design is required.

Etching (Chemical Corrosion)

Process: Using strong acid or laser to corrode patterns or text on the surface, creating a raised and recessed effect.

Characteristics: Customizable patterns, suitable for artistic decorations, signboards, etc. 

II. Surface Treatment Process of Stainless Steel Water Pipes

1. Cleaning and Anti-Rust Foundation Treatment

Mechanical Polishing (Inner and Outer Wall Polishing)

Process: The inner wall is polished using a dedicated polishing head or abrasive balls, while the outer wall is polished with a sand belt, ensuring that the roughness of the inner and outer surfaces is Ra ≤ 0.8 μm (for drinking water pipes, Ra ≤ 0.4 μm).

Features: The inner wall is smooth to reduce fluid resistance and bacterial adhesion, and the outer wall is aesthetically pleasing and easy to clean. This is the basic process for water pipes.

Passivation Treatment (Acid Washing Passivation)

Process: Use nitric acid, hydrofluoric acid, etc. to remove surface oxide scale and form a passivation film (main component is Cr₂O₃), enhancing corrosion resistance.

Features: Remove the oxide layer and impurities after welding to ensure the material meets hygiene standards, often used for food-grade water pipes.

2. Functional Protective Process

Electrolytic Polishing (Electrochemical Polishing)

Process: The pipe is used as the anode and immersed in an electrolyte solution, with electricity passed through to dissolve the microscopic protrusions on the surface, achieving a mirror-like effect (Ra ≤ 0.2 μm).

Features: The surface is smoother and denser, with better corrosion resistance than mechanical polishing, suitable for high-purity fluid transportation (such as in the pharmaceutical and beverage industries).

Chromium-Free Passivation (Environmental Protection Treatment)

Process: Use titanium salts, silanes, etc. as chromium-free agents instead of traditional acid washing to form a protective film, meeting environmental protection standards (such as the EU RoHS Directive).

Features: Avoids hexavalent chromium pollution and is suitable for drinking water pipes and scenarios with strict environmental requirements.

3. Special Scene Treatment

Antibacterial Treatment (Nano Coating)

Process: Apply a coating containing silver ions, zinc oxide, etc. of antibacterial agents on the surface to inhibit bacterial growth.

Features: Commonly used in drinking water systems in hospitals and schools with high hygiene requirements.

Anti-scaling Treatment

Process: Through chemical plating or surface modification, reduce surface tension and reduce calcium and magnesium ion deposition.

Features: Suitable for areas with hard water, extending the service life of water pipes. 

III. Comparison of the Two Processes and Core Differences

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IV. Application Examples

Decorative Pipe Craftcase:

The stainless steel door frames of hotel revolving doors are usually treated with 8K mirror polishing and titanium-plated rose gold coating, which not only gives a luxurious appearance but also resists daily friction; outdoor guardrails mostly use sandblasting + fluorocarbon spraying, balancing rust prevention and weather resistance.

Water Pipe Craftcase:

The drinking water pipes in residential areas use 316L stainless steel + inner and outer wall electrolytic polishing + passivation treatment to ensure pure water quality; industrial chemical pipes need electrolytic polishing + chrome-free passivation to prevent leakage of corrosive fluids. 

Summary: The surface treatment of decorative pipes is "priority given to appearance", while water pipes are "function-oriented". The core difference in the choice of manufacturing processes between the two stems from the different requirements of "decorativeness" and "safety".