1. What Material is C22000?
Optimal Formability: Easily drawn, stamped, bent, rolled, and brazed/welded, making it suitable for complex fabrications (e.g., deep drawing, spinning).
Good Mechanical Strength: Balances tensile strength (300–500 MPa, depending on temper) and ductility (elongation up to 60% in annealed state), outperforming pure copper in load-bearing applications.
Corrosion Resistance: Resists tarnishing and mild corrosion in atmospheric, fresh water, and neutral saltwater environments; however, it is not recommended for harsh corrosive media (e.g., strong acids, ammonia) due to potential dezincification (zinc leaching) under extreme conditions.
Cost-Effectiveness: Offers better strength-to-cost ratio than pure copper (e.g., C11000) by replacing copper with zinc, without significant loss of workability or aesthetic appeal.
Compared to C26000 (70/30 brass), it has higher copper content, better ductility, and lower strength.
Compared to C23000 (red brass, 85% Cu), it has higher zinc content, improved machinability, and a brighter gold color.
2. What is the Surface Color of C22000?
2.1 As-Fabricated/Annealed State
Freshly processed (e.g., extruded, rolled, annealed) C22000 exhibits a bright, warm golden-yellow or pale gold color. This is the alloy's inherent color, resulting from the optical properties of its copper-zinc solid solution (≈90% Cu imparts a warm base tone, while 10% Zn lightens the hue to gold).
Machined or polished surfaces have a high-gloss golden finish (similar to 14K gold), making it popular for decorative and architectural applications.
2.2 Natural Oxidation/Tarnish
Initial Stage (1–3 months): The bright gold surface fades to a dull golden-brown or bronze-like tan as a thin copper oxide (Cu₂O) layer forms.
Intermediate Stage (6–12 months): With prolonged exposure, the tarnish deepens to a dark brown or light brownish-green (mixed copper-zinc oxides and hydroxides).
Mature Stage (1+ years): In humid or coastal environments, the surface may develop a thin, patchy greenish patina (similar to pure copper but lighter in tone), though this process is slower than pure copper due to the zinc content.
2.3 Post-Treatment/Coating
Polished & Lacquered: A clear lacquer coating preserves the bright gold color indefinitely, preventing oxidation.
Electroplated: Common finishes include nickel plating (silver-white), chrome plating (mirror-like silver), or gold plating (enhanced golden hue) for corrosion resistance or aesthetic customization.
Chemical Patination: Controlled chemical treatments can produce uniform colors such as dark brown, antique green, or black for decorative or architectural purposes (e.g., antique furniture hardware, architectural trim).
2.4 Heat-Treated State
When heated to 300–500°C, C22000 forms a dark brown or black oxide layer (mixture of CuO and ZnO) on the surface. This layer can be removed via polishing or pickling to restore the original gold color.
