Troubleshooting Electrophoretic Lacquer

EPA 2020

EPA Lacquer 2020 is a water-based electric lacquer available in clear or various colors as needed. It provides a superior coating compared to traditional spraying or dipping methods. The resulting finish is durable and suitable for various types of jewelry.

Characteristics of the Solution:

• Glossy and clear electric lacquer

• Thin, shiny, and sparkly coating

• Does not form droplets on the item

• Water-based, low in toxicity, and safe to use

• Can be handled after application due to high durability

• Suitable for coating metal or plated surfaces, such as silver, brass, jewelry pieces, decorative items, and more

Working Procedure:

To reduce metal contamination and impurities, distilled water should be used for rinsing before and after applying the lacquer.

1. Items to be coated

2. Rinse with distilled water twice

3. Dip to adjust the surface with 2% Lacquer 2020

4. Coat the surface with Lacquer 2020 using electricity

5. Rinse with distilled water twice

6. Dip in a water stain remover

7. Blow dry

8. Bake the items

Working Conditions:

• Teknoclear EPA 2020: 330 g/L

• Dye (Optional): 0 - 1 ml/L

• RI: 12 - 14

• pH: 4.4 - 5.2

• Conductivity: 900-1100 μs

• Solvent: 3 – 4%

• Temperature: 23 - 27 °C

• Electrode: Stainless steel, grade 316

Current:

• 0.05 - 0.1 A/dm²

• 30-50 V

• Electrode to item area ratio: 2 / 1

• Coating rate: 8 microns (within the first 30 seconds)

• Time: 10 - 120 seconds

• Pre-current time: 10-15 seconds

Curing:

• Curing Temperature: 150 - 180 °C

• Curing Time: 20 minutes

For some cases, such as zinc plating, high-temperature curing may cause blistering. For lower temperatures, increase curing time:

• Curing Temperature: 120 - 140 °C

• Curing Time: 30 minutes

Note: Insufficient curing can result in a soft lacquer finish and potential fingerprint marks if the lacquer does not dry properly.

Solution Mixing:

1. Mix Lacquer 2020 with lacquer dye (if applicable) until homogeneous.

2. Gradually add distilled water while stirring until the solution is full.

3. Stir the solution continuously for at least 12 - 24 hours.

4. Ready for use.

(The distilled water used should have a conductivity of less than 5 μs.)

If using lacquer dye, mix the dye outside the bath first before adding it to the bath.

Lacquer 2020 Mixing Ratios:

Recommended Standard

Lacquer 2020 33% ----- 30 - 35%

Lacquer Dye 1% ----- 0.8 - 1.5%

After adding lacquer or other additives, stir the solution for at least 15 - 30 minutes before use.

Adjusting the Solution:

• RI: Check the RI using a refractometer; it should be around 11 - 14. To increase the RI by 1 unit, add 33 cc of lacquer per liter.

• Solvent: Check RI of the solution from the ultrafiltration outlet using a refractometer; it should be around 0.8 - 2.0. If the RI is below 0.8, add Flow Additive (1 - 2 ml/L). If above 2.0, filter the solution (ultrafiltration).

• Conductivity: Check conductivity with a conductivity meter; it should be 900 – 1000 μs. If above 1000 μs, filter the solution (ultrafiltration) or add lacquer (20 g/L).

• pH: Check pH with a pH meter; it should be around 4.2 to 5.2. If outside this range, there may be contamination. Filter the solution (ultrafiltration) and use Emulsion Stabilizer if needed. If pH is low, filter the solution (ultrafiltration) and discard solution from the filter tube. If pH is high, adjust with Emulsion Stabilizer as per MEQ value.

• MEQ: Check MEQ by titrating with 0.1 M KOH; it should be 27 - 33. To increase MEQ by 1 unit, add stabilizer (0.1 cc/L). If MEQ is low, adjust with Emulsion Stabilizer. If high, filter the solution (ultrafiltration) and discard solution from the filter.

Additives:

• Flow Additive: Necessary for maintaining bath concentration; total concentration should be 3 - 4%.

• Stabilizer: Though important, it does not need frequent use; add 0.2-0.3 cc/L as needed to maintain pH and MEQ.

Equipment:

• Lacquer Bath: Use PP or PVC bath with stirring system.

• Solution Pump: Must stir the solution at least 5 times the bath size per hour and have a 1 - 3 microns filter.

• Electrode Plates: Use stainless steel, grade 316.

• Ultrafiltration: Used to control lacquer conductivity.

• Power Supply: Should be adjustable up to 60 volts.

• Drying Oven: For baking items.

Troubleshooting Guide:

1. Thick Lacquer Film:

   • Excessive current: Reduce current.

   • Long immersion time: Reduce immersion time.

   • Excessive solvent: Filter using ultrafiltration.

2. Wrinkled Lacquer Film (Orange Peel Effect):

   • Excessive solvent: Filter using ultrafiltration.

   • Rapid or excessive current: Reduce current.

3. Thick and Uneven Lacquer Film:

   • Rapid or excessive current: Reduce current to less than 0.5 A/dm².

   • High temperature: Reduce temperature.

   • Contaminated solution: Filter using ultrafiltration.

4. Thin Lacquer Film:

   • Insufficient lacquer: Analyze and adjust.

   • Low current: Increase current.

   • Short immersion time: Increase immersion time.

5. Thin Lacquer Film with High Voltage Stripes:

   • Insufficient solvent: Analyze and adjust.

   • Insufficient lacquer: Add more lacquer.

   • Low temperature: Adjust temperature to 25-30 °C.

6. Iridescent Lacquer Film:

   • Insufficient lacquer: Add more lacquer or analyze and adjust.

   • Low temperature: Increase heat in the bath.

   • Low current: Increase current.

   • Short immersion time: Increase immersion time.

7. Patchy Thin Lacquer Film:

   • Incorrect concentration: Adjust or analyze and adjust.

   • Low pH: If pH is below 4.2, filter using ultrafiltration.

8. Pitting or Spotting on Lacquer Film:

   • Contaminated items: Remove grease, oil, polish, or impurities from the surface.

   • Contaminated solution: Filter using ultrafiltration.

   • Sediment in solution: Filter solution and possibly use ultrafiltration.

   • Poor quality rinse water: Use water with conductivity less than 5 microsiemens.

9. Stains on Items After Rinsing:

   • Excessive solvent: Filter using ultrafiltration.

10. Stains on Items After Baking:

    • Inadequate rinsing: Increase rinse water and agitation.

    • Poor drying: Use clean, dry air.

    • Use water stain remover with final rinse.

11. Gas Bubbles or Bubble Marks:

    • Gas bubbles in the solution: Turn off the pump and wait until the solution clears.

    • Poor surface preparation: Increase rinsing time.

12. Weak Lacquer Film:

    • Low curing temperature: Increase baking time for heat-sensitive items.

13. Light Brown or Yellow Solution:

    • Lacquer settling due to heat: Check solution agitation and filtration.

    • High temperature: Adjust to 25-30 °C.

14. Decreasing Amperage During Coating:

    • Excessive solvent: Filter using ultrafiltration.

    • High pH: Alkalinity contamination from rinse water; filter using ultrafiltration.

    • Metal contamination: Remove impurities.

15. Low Conductivity:

    • Insufficient lacquer: Add more lacquer or analyze and adjust.

    • Low solvent: Adjust solvent concentration.

16. High Conductivity (>1300 microsiemens):

    • Excessive lacquer: Reduce current.

    • Excessive solvent: Filter using ultrafiltration.

    • Contaminated solution: Filter using ultrafiltration.