This is the "Barrel Plating Post-Treatment & Lacquering Operations Manual".

The Master's Reality: You can plate the most beautiful mirror-bright Gold or Gunmetal, but if your Post-Treatment is wrong, it will turn brown in 24 hours (Oxidation) or look like cheap plastic after Lacquering (Loss of Metallic Luster).

The Goal: To seal the metal against corrosion (Salt Spray Test) while keeping the finish looking "Wet" and "Metallic," not "Plasticky."

Here is the Master’s Standard for the finishing stage using the [QLQ System].

🛡️ Barrel Post-Treatment & Lacquering Manual (The Final Shield)

Target: Zinc Alloy & Brass Zipper Pulls, Buttons.

Goal: 24-48 Hour Salt Spray Test (NSS) Pass + Crystal Clear Gloss.

Key Challenge: Preventing "Water Stains" and "Lacquer Fog."

Part I: The Rinse & Neutralization Sequence (Crucial)

You cannot lacquer dirty parts. 90% of spots come from plating salt residue.

Step 1: Counter-Flow Rinsing (3-Stage)

• Rule: Do not rinse in stagnant water.

• Technique:

  • Tank 1 (Dirty): Captures 90% of drag-out.

  • Tank 2 (Clean): Dilution.

  • Tank 3 (Pure): RO Water (Reverse Osmosis). Conductivity < 20 µS.

• Master's Tip: If you use tap water in the final rinse, the Calcium/Magnesium leaves white "water spots" under the lacquer.

Step 2: Neutralization (The pH Balance)

• For Acid Plating (Nickel/Gunmetal):

  • Dip in weak Alkali (10 g/L Sodium Carbonate) $\rightarrow$ Rinse.

• For Cyanide Plating (Gold/Brass/Copper):

  • Dip in weak Acid (1% Citric Acid) $\rightarrow$ Rinse.

• Why? Trapped acid/alkali in the zipper hole will bleed out later and eat the lacquer.

Step 3: Passivation (The Chemical Seal)

• Application: Essential for Brass, Imitation Gold, and Zinc finishes.

• Formula: [QLQ] Cr3+ Passivate (Clear).

• Time: 15 – 30 seconds.

• Visual: The surface should remain bright. If it turns "Rainbow/Iridescent," the concentration is too high (looks cheap).

Part II: The Drying Process (Centrifuge Logic)

Before lacquering, the part must be perfectly dry. Water + Lacquer = White Fog.

The Centrifuge SOP:

1. Load: 15 KG Max. Balance the basket.

2. High-Speed Spin (No Heat): 2 mins at 800 RPM.

   • Why? Throw the water off mechanically first.

3. Heat Spin: Turn on heater (80°C). Spin 3 mins.

4. Cool Down: Run fan for 1 min.

   • Rule: Do not dump hot parts into a pile. They will sweat.

Part III: Barrel Lacquering (The "Gloss" Saver)

This is where most factories fail. They apply lacquer too thick, killing the metallic reflection.

The Equipment: Dip-Spin Coating Machine (Centrifugal Coater).

1. Material Selection (The "Invisible" Lacquer)

• Option A: Water-Based Acrylic (Eco-friendly)

  • Pros: Cheap, no fire risk.

  • Cons: Can look cloudy if applied thick.

• Option B: Solvent-Based Epoxy/PU (High Performance)

  • Pros: Highest Gloss, thinner film, better adhesion.

  • Cons: Flammable smell.

• QLQ Recommendation: [QLQ] High-Gloss Nano-Lacquer (Waterborne). It is formulated with a Refractive Index matching metal, so it disappears visually.

2. The Viscosity Secret (Ford Cup #4)

• The Error: Using lacquer straight from the drum (Too thick > 30s).

• The Master's Standard:

  • Target: 10 – 12 Seconds. (Like milk).

  • Why? A thin viscosity allows the lacquer to wet the surface instantly and spin off cleanly without "Orange Peel."

  • Formula: 1 Part Lacquer : 1 Part Thinner/Water.

3. The "Pulse Spin" Technique (SOP)

• How to coat without sticking or drip marks:

1. Dip: Submerge basket in lacquer tank. Lift up.

2. Slow Spin: 50 RPM for 10 seconds (Distribute liquid).

3. Fast Spin (The Throw):

   • Forward: 600 RPM for 20 seconds.

   • Reverse: 600 RPM for 20 seconds.

   • Why Reverse? To remove the "tear drop" of lacquer hanging on the bottom of the zipper pull.

Part IV: Curing (Baking) Parameters

Undercured = Sticky. Overcured = Yellow.

• Master's Trick: "Step-Baking."

  • 10 mins at 60°C (Flash off solvent) $\rightarrow$ 20 mins at 130°C (Cure).

  • Result: Prevents solvent boil (bubbles) and ensures glass-smooth finish.

Part V: Master’s Troubleshooting (Gloss Protection)

Part VI: Efficiency & Cost Control

1. Lacquer Recycling

• Issue: Lacquer in the dip tank thickens over time (solvent evaporation).

• Action:

  • Every 2 hours, add thinner to restore viscosity to 11 seconds.

  • Every week, filter the lacquer through a 200-mesh screen to remove dust/lint.

2. Anti-Tarnish vs. Lacquer

• Cost Saving: For cheap items (Iron base), use [QLQ] Nano Anti-Tarnish Dip instead of Lacquer.

• Cost: 10% of lacquer cost.

• Performance: Good for shelf-life, bad for wear resistance.

• Appearance: 100% Metallic (Invisible layer).

🌟 Featured Album: The "Invisible Shield" Series

Description for the Blog/Guide Album:

🛡️ The "Invisible Shield" Album: Protecting Gloss Without Killing It

The customer wants "Shiny Metal," not "Shiny Plastic." The Post-Treatment line is where you define the final luxury feel of the product.

What you will master:

• 💧 The Viscosity Law: Why mixing your lacquer to 11 Seconds (Ford Cup) is the only way to get that "Wet Look" without the plastic thickness.

• 🌀 The "Pulse Spin" Hack: A video demonstration of the Forward/Reverse spin technique that eliminates those ugly dried drips at the bottom of your zipper pulls.

• 🌈 Stopping the Rainbow: How to tune your Passivation dip so it protects the Brass without creating that cheap-looking iridescent oil-slick effect.

• 🌡️ The "Safe Heat" Chart: A printable guide on the maximum baking temperatures for White Bronze, Gold, and Gunmetal to prevent discoloration.