Zinc products Rack plating work shop

Phase I: Racking & Pre-treatment (Critical for Adhesion & Springs)

Step 0: Racking (Cage Loading)

• Action: Load 600 pcs into the Cage Rack. Ensure strict contact but allow minimal movement to prevent shading marks.

• Check: Ensure stainless steel springs are not over-compressed.

Step 1: Hot Soak Degreasing (Removal of Wax/Oil)

• Chemicals:

  • [QLQ Product] Zinc Liquid Dewaxing Agent: 50–80 ml/L.

  • [Purchase Locally] Sodium Hydroxide: (Only if pH adjustment needed, keep low).

• Parameters:

  • Temp: 65–75°C.

  • Time: 5–8 mins.

  • Agitation: Mechanical Rocker + Ultrasonic (Recommended).

• Note: Solution must be filtered continuously to remove oil sludge.

Step 2: Counter-current Rinse (2-Stage)

Step 3: Cathodic Electro-cleaning (The "Safe" Clean)

• Chemicals:

  • [QLQ Product] Zinc Electro-cleaning Salt: 40–60 g/L (No etching on Zinc).

• Parameters:

  • Temp: 50–60°C.

  • Voltage: 4–6 V.

  • Time: 30–60 seconds.

  • Polarity: Workpiece as Cathode (-).

  • Anode: Stainless Steel Plate (316L).

• Warning: Never use Anodic (+) cleaning for zinc; it will destroy the surface and the springs.

Step 4: Weak Acid Activation (Anti-Embrittlement)

• Chemicals:

  • [QLQ Product] Acid Activation Salt: 15–20 g/L (Fluoride-based).

  • [Purchase Locally] Sulfuric Acid: 0.5% (Optional, minimal).

  • Strictly Forbidden: Hydrochloric Acid (HCl).

• Parameters:

  • Temp: Room Temperature.

  • Time: 5–15 seconds (Until light bubbling).

• Note: This step neutralizes the alkali film without penetrating the stainless steel grain boundaries.

Phase II: Base Plating (Leveling & Protection)

Step 5: Cyanide Copper Strike (Barrier Layer)

• Chemicals:

  • [Purchase Locally] Copper Cyanide: 45–50 g/L.

  • [Purchase Locally] Sodium Cyanide: 60–70 g/L.

  • [Purchase Locally] Rochelle Salt: 40–50 g/L.

• Parameters:

  • Temp: 50–55°C. pH: >12.5.

  • Current: Start at 3 A/dm² for 1 min, then 1.5 A/dm².

  • Time: 10–15 mins (Thickness > 5µm).

  • Filtration: Continuous.

• Live Entry: Rack must enter with current ON to prevent immersion copper.

Step 6: Acid Dip (Neutralization)

• Chemicals: [Purchase Locally] Sulfuric Acid (5%).

Step 7: Acid Copper Plating (The "Mirror" Finish)

• Chemicals:

  • [Purchase Locally] Copper Sulfate: 200–220 g/L.

  • [Purchase Locally] Sulfuric Acid: 55–65 g/L.

  • [Purchase Locally] Chloride Ion: 60–80 ppm.

  • [QLQ Product] Acid Copper Brightener (B): High leveling.

  • [QLQ Product] Acid Copper Make-up (Mu).

• Parameters:

  • Temp: 22–26°C (Chiller Mandatory).

  • Current: 3–4 A/dm².

  • Time: 20–25 mins.

  • Agitation: Air Agitation (Oil-free blower) is required for high brightness.

  • Anode: Phosphorized Copper Balls in Titanium Baskets.

Step 8: Bright Nickel Plating (White Base)

• Chemicals:

  • [Purchase Locally] Nickel Sulfate: 280–300 g/L.

  • [Purchase Locally] Nickel Chloride: 50–60 g/L.

  • [Purchase Locally] Boric Acid: 40–45 g/L.

  • [QLQ Product] Nickel Softener: High Dosage (To prevent spring cracking).

  • [QLQ Product] Nickel Brightener: Consult QLQ.

• Parameters:

  • Temp: 55–60°C. pH: 4.0–4.8.

  • Current: 3–4 A/dm².

  • Time: 10–15 mins.

Phase III: Color Finishes (Split by Batch)

At this stage, the production line splits into different tanks for final color.

Option A: Imitation Gold (Light Gold)

• Chemicals: [QLQ Product] Imitation Gold Salts (Brass Alloy).

• Parameters: 35–40°C, 2–4 Volts, 20–40 seconds.

• Note: Requires Gold-color Anodes (Brass) or Stainless Steel.

Option B: Rose Gold

• Chemicals: [QLQ Product] Rose Gold Premix.

• Parameters: 45–50°C, 30–50 seconds.

• Note: Highly temperature sensitive. Use a heater with precise $\pm 1$°C control.

Option C: Gunmetal / Black Nickel (Tin-Nickel Alloy)

• Chemicals: [QLQ Product] Gunmetal Salts.

• Parameters: 60–65°C, pH 2–3, 3–5 mins.

• Note: Superior wear resistance compared to traditional sulfide black nickel.

Option D: White Nickel (Silver Color)

• Process: Stop after Step 8, then Chrome Flash or Passivate directly.

• Or: Use [QLQ Product] White Bronze for a Nickel-Free Silver look.

Option E: Antique Bronze (Qing Gu Tong)

• Process:

  1. Plate Heavy Copper or Brass (10 mins).

  2. Dip in [QLQ Product] Black Oxidizer (1-2 mins) $\rightarrow$ Parts turn black.

  3. Mechanical Brushing: Remove parts from rack. Use a Brushing Machine (Scotch-Brite wheel) or Tumbler to remove the black from highlights, revealing bronze color.

  4. Re-rack for Lacquering.

Phase IV: Post-Treatment (The Quality Guarantee)

Step 9: Electrolytic Passivation (Chromate)

• Chemicals: [QLQ Product] Electrolytic Passivation Salt.

• Parameters: Room Temp, 30 seconds.

• Purpose: Removes organic film and seals the surface.

Step 10: Hot Water Rinse (60-80°C) – Aids drying.

Step 11: Hydrogen Relief Baking (MANDATORY)

• Timing: IMMEDIATE (Transfer from line to oven within 1 hour).

• Equipment: Tunnel Oven or Batch Oven.

• Parameters: 180°C for 3 Hours.

• Reason: This bakes out the hydrogen absorbed during electro-cleaning and pickling. Without this, the stainless steel spring inside the zipper head will snap after 1-2 months.

Step 12: Rack Lacquering (Sealing)

• Method: Dip Lacquer or Electrophoretic Lacquer (E-Coat).

• Chemicals: [QLQ Product] Clear Acrylic Lacquer.

• Curing: 120°C for 30 mins.