Troubleshooting Hard Chrome

Decorex Conducting Salt

Decorex Conducting Salt is a chemical powder designed to enhance the performance of chromium plating baths, particularly in low-current areas. It improves the adhesion, thickness, and gloss of the chromium coating in these low-current regions, making them comparable to high-current areas.

Usage Instructions

• Chromic Acid: 230-250 grams/liter

• Sulfuric Acid: 1.8-3.4 cc/liter

• Decorex Conducting Salt: 5-15 grams/liter

• Density of Solution: 22-26 degrees Baumé

• Temperature: 55-60°C

• Current Density at Cathode: 15-25 amps/dm²

• Current Density at Anode: 5-10 amps/dm²

Note: Ensure that a fume extraction system is in place.

Example for Bath Use

For a 100-liter bath, add 500 grams of Decorex Conducting Salt. Dissolve the powder in distilled water first until fully dissolved, then slowly add to the bath while stirring thoroughly.

Equipment

• Tank: Steel tanks lined with lead or flexible PVC are suitable. Ensure the tank has a fume extraction system. For heating, use a silica heater or titanium heating coil, as the temperature increases during continuous operation. Include a cooling system, such as titanium or lead coils or a cooling stack.

Maintenance

• Concentration Control: Monitor solution concentration using a density meter. Regularly analyze the solution, focusing on chromic acid and sulfate levels. To increase sulfate, use chromic acid powder; to decrease sulfate, use Barium Hydroxide or Barium Carbonate.

Caution: Chloride ions are harmful to chromium plating baths, so avoid introducing chlorides via rinsing water.

Using Barium Carbonate to Reduce Sulfuric Acid in Chrome Plating Baths

In chrome and hard chrome baths, which contain chromic acid and sulfuric acid in a 100:1 ratio, excess sulfuric acid can cause yellowing and poor coverage. To reduce sulfuric acid:

1. Dissolve Barium Carbonate in distilled water until fully dissolved.

2. Slowly add to the bath while stirring (beware of vigorous reactions and gas bubbles).

3. Allow the solution to settle overnight.

4. Warm the solution and perform a dummy run before use.

5. Optionally, clean the tank if sediment accumulates at the bottom.

Recommendations:

• Avoid adding Barium Carbonate in large amounts at once to prevent solution imbalance.

• Allow sediments to settle before using the solution.

• Adjust Barium Carbonate quantities based on actual conditions and consider adding more chromic acid if needed.

Troubleshooting for Hard Chrome Plating Solution

1. Problem: Poor Adhesion

   • 1.1: Inadequate cleaning. Verify cleaning methods and degreasing solutions to ensure effectiveness. Check for oil or grease residues.

   • 1.2: Rust or oxide on workpieces. Check cleaning methods and degreasing solutions.

   • 1.3: Electrical issues. Ensure a consistent electrical current; pre-soak in chromic acid solution if needed.

   • 1.4: Poor adhesion of intermediate layers. Ensure previous metal layers, such as nickel, are well-attached.

2. Problem: Poor Plating Coverage

   • 2.1: High sulfate concentration. Analyze and adjust sulfate levels using Barium Carbonate.

   • 2.2: Temperature above 65°C. Adjust temperature to the correct range.

   • 2.3: Low solution concentration. Increase the concentration.

   • 2.4: Low current density. Adjust current density to 50-60 A/dm².

   • 2.5: Iron contamination. Dilute the solution to reduce contaminants.

3. Problem: Rough Surface

   • 3.1: Suspended solids in solution. Allow sediments to settle, then clean the tank.

   • 3.2: Dirty cathode surface. Avoid carbon smut; remove dust and dirt.

   • 3.3: Overcurrent. Reduce current density and prevent accumulation.

   • 3.4: Rough or contaminated pre-plated surface. Polish the surface or use electropolishing.

4. Problem: Burned Surface

   • 4.1: Low temperature. Adjust the temperature.

   • 4.2: Low chemical density. Increase the density.

   • 4.3: High current density. Reduce current density.

5. Problem: Surface Defects (Spots or Marks)

   • 5.1: Inadequate cleaning. Verify cleaning methods and check for oil or grease residues.

   • 5.2: Trapped air bubbles. Reduce workpiece density or add additional anodes.

6. Problem: Incomplete Plating

   • 6.1: Low current density. Increase voltage to achieve higher current density without burning.

7. Problem: Dull Color

   • 7.1: Incorrect temperature-current relationship. Increase temperature if too low or decrease current density if too high.

8. Problem: White Surface

   • 8.1: High temperature relative to current density. Reduce temperature and adjust current density.

9. Problem: Incomplete Plating in Areas

   • 9.1: Possible nickel plating issues. Ensure thorough nickel plating before hard chrome.

   • 9.2: Solution imbalance. Analyze and correct.

   • 9.3: Uneven current distribution. Space workpieces properly and adjust anodes.

   • 9.4: Reduced performance due to solution cooling. Increase current density if needed.

   • 9.5: High trivalent chromium. Increase anode surface area to convert trivalent to chromic acid.

   • 9.6: Air bubbles. Reduce workpiece density or add additional anodes.

10. Problem: Electroplating does not adhere to the workpiece surface. 

    • 10.1: Electrical issues. Check for proper connections, clean contacts, and ensure correct polarity.

    • 10.2: HCl contamination. Avoid contamination and remove chlorides.

11. Problem: Poor Current Flow

    • 11.1: High temperature. Adjust temperature.

    • 11.2: Low solution density. Increase density by adding chromic acid.

    • 11.3: Excess sulfuric acid. Reduce by adding Barium Carbonate.

    • 11.4: Low current density. Adjust and measure current density.

    • 11.5: Contamination with bivalent and trivalent metals. Perform a dummy run or adjust anode-cathode relations.

    • 11.6: Chloride contamination. Avoid contamination and clean thoroughly after nickel plating. Perform analysis if needed.