Xiamen Uni-Green Industries CO., LTD.
26
2025
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05
Champagne Bronze Process
Author:
Champagne copper is a surface effect with an elegant metallic texture, and its surface treatment process needs to combine the characteristics of the metal substrate with color presentation requirements. Below is a common champagne copper surface treatment process flow and key points, with the spray painting process and chemical coloring removed:
I. Substrate Pretreatment
1. Degreasing
- Purpose: Remove organic substances such as oil stains, fingerprints, and wax from the substrate surface to ensure the adhesion of subsequent coatings.
- Methods:
- Chemical degreasing: Use alkaline solutions (such as sodium hydroxide, sodium carbonate) or specialized metal degreasing agents, processed by immersion, ultrasonic, or spray methods.
- Electrolytic degreasing: The substrate acts as an electrode, 通电 (electrified) in an alkaline solution, with grease peeled off by bubbles (suitable for stainless steel, aluminum alloy, etc.).
2. Surface Cleaning and Activation
- Purpose: Remove oxide films, rust, and microscopic impurities to activate the substrate surface.
- Methods:
- Mechanical sandblasting: Sandblast the substrate with quartz sand, glass beads, etc., to form a rough surface (suitable for metals like aluminum and iron).
- Pickling/alkaline cleaning:
- For steel substrates: Use hydrochloric acid or sulfuric acid to remove rust (control time to avoid over-etching).
- For aluminum/copper substrates: Use sodium hydroxide solution to remove the oxide film, then neutralize with nitric acid.
- Water rinsing: Thoroughly flush residual chemical solutions to prevent contamination of subsequent processes.
II. Champagne Copper Color Layer Construction (Electroplating Process)
The color effect of champagne copper is most commonly achieved through electroplating. Here is the core process:
1. Pre-plating Underlayer
- Purpose: Enhance the adhesion between the substrate and the copper coating (especially for non-copper substrates like stainless steel and zinc alloy).
- Process:
- Nickel plating: Use acidic nickel plating or nickel aminosulfonate process with a coating thickness of 1-3μm to provide a smooth base.
- Copper plating (optional): For iron substrates, first plate a layer of cyanide copper or pyrophosphate copper to prevent substrate corrosion.
2. Electroplating Champagne Copper Alloy
- Core coating: Achieve the champagne color through electroplating a ternary alloy of copper-tin-zinc (or copper-nickel-zinc).
- Composition of electroplating bath:
- Main salts: Cuprous cyanide (provides copper ions), zinc sulfate (provides zinc ions), sodium stannate (provides tin ions).
- Complexing agents: Sodium cyanide (stabilizes metal ions), sodium hydroxide (adjusts pH).
- Additives: Organic brighteners (such as benzylidene acetone, alkynol derivatives) to control coating color and brightness.
- Process parameters:
- Temperature: 25-40°C, current density: 1-3A/dm², pH: 8-10, time: 5-15 minutes.
- Color control:
- Higher copper content: Tendency to red-gold; higher zinc/tin content: Tendency to yellow-white. Adjust the bath composition to achieve the champagne color balance.
3. Post-treatment (Sealing and Protection)
- Passivation treatment:
- Chemical passivation: Use chromate (requires eco-friendly alternatives) or chromium-free passivators (such as titanium salts, silanes) to form a protective film and prevent oxidation and discoloration.
- Electrolytic passivation: Treat in dilute chromic acid solution with electricity to enhance corrosion resistance.
- Coating protective layer:
- Spray transparent varnish (acrylic, polyurethane, etc.) with a thickness of 5-10μm to improve scratch resistance and weatherability.
- Electroplate transparent nickel or chromium (thickness 0.1-0.3μm), suitable for high-wear scenarios (such as bathroom hardware).
III. Surface Effect Treatment (Optional)
1. Brushing/Polishing
- Brushing: Use sandpaper, scouring pads, or brushing machines to create directional patterns on the coating surface, enhancing texture (such as straight lines, random lines).
- Polishing: Mechanical polishing or electrolytic polishing to improve surface flatness and gloss (suitable for high-gloss champagne copper effects).
2. Antique Aging
- After electroplating, slightly corrode the surface with an acidic solution (such as nitric acid) or apply potassium sulfide solution to form a mottled oxide layer, creating a retro champagne copper effect.
IV. Quality Inspection and Control
- Adhesion test: Cross-cut method (ISO 2409) to check if the coating peels off.
- Corrosion resistance test: Salt spray test (ASTM B117), requiring no rust or discoloration after 48 hours of neutral salt spray.
- Color consistency: Use a color difference meter (such as CIE Lab*) to compare with the standard color plate, with ΔE＜1.5 as qualified.
- Hardness test: Pencil hardness method (ISO 15184), requiring the coating hardness to be ≥2H.
V. Common Issues and Solutions
|
Issue |
Cause |
Cause |
|
Uneven color |
Uneven electroplating bath temperature/current density
|
Strengthen stirring and regularly filter the plating solution |
|
Coating peeling |
Incomplete pretreatment or insufficient underlayer adhesion |
Increase sandblasting roughness and adjust the pre-plating process |
|
Poor corrosion resistance |
Thin passivation film or insufficient varnish thickness |
Extend passivation time and increase the number of varnish spraying passes |
|
Low gloss |
Insufficient electroplating additives or low spraying air pressure |
Supplement brighteners and adjust spraying equipment parameters |
Application Scenarios
Champagne copper surface treatment is widely used in bathroom hardware, furniture handles, electronic product casings, automotive trims, architectural decorations, etc. Its warm tone and metallic texture enhance product grade, while diversified surface effects (such as matte, high-gloss, brushing) can be achieved through process combinations.
If you need to design processes for specific substrates (such as stainless steel, aluminum alloy), please further provide the substrate type and performance requirements to optimize process details.
If you encounter problems with the electroplating process or have electroplated products that need to be processed, you're welcome to contact us.