1. Industry Background:

After many technological developments, electroplating hard chrome remains an irreplaceable main process. However, due to the limitations of raw material purity and process flow, the plating solution cannot maintain a high purity level. As the usage time extends, the quality of electroplating will gradually decrease.
 

    According to authoritative literature, the impact of copper and iron impurities on chrome plating quality is significant. When the total content exceeds 1.2g/L, the wear resistance and corrosion resistance of the chrome layer will decrease. When the total content exceeds 2.5g/L, the brightness range and hardness of the chrome layer will be significantly affected, while the bath voltage will increase and current efficiency will decrease. When the total content exceeds 5g/L, the comprehensive indicators of the chrome layer can only reach half of that of a newly opened tank. When the impurity content in the plating solution exceeds the standard, especially in the relatively high temperature and humidity of summer, the comprehensive defects of the chrome layer are more likely to be exposed, leading to a significant increase in external return. Therefore, many manufacturers of high-end chrome solutions need to regularly dilute the solution to reduce the content of impurity ions.
 

1.1 Hazards of Excessive Impurities
Hazard 1
Slow deposition speed of the coating, increased energy consumption
Hazard 2
Increased porosity of the coating, reduced corrosion resistance
Hazard 3
Reduced dispersion ability of the coating, decreased brightness
Hazard 4
Changes in the structure of the coating, reduced hardness, decreased wear resistance

1.2 Sources of Impurities in the Plating Solution
Main Raw Materials:
Main Sources

• Using inferior chromic anhydride and sulfuric acid leads to the accumulation of impurities.
• High-quality raw materials should be selected as much as possible.
   

Workpiece Contamination:

• Rust on the plate not cleaned properly is brought in.
• During the preheating process of the plate roller, the plating solution corrodes the copper layer.
• Leakage.

Equipment Corrosion:

• Conductive copper bars, screws, and hanging tools are corroded by chrome mist, and residual liquid drips into the plating tank.
• Corrosion debris from the equipment shell falls into the plating tank.

Anode Purity:

• Insufficient anode purity leads to abnormal dissolution or corrosion.

2. Solutions
Cationic Resin Exchange Method
The plating solution needs to be diluted to below 50g/L for processing, and the concentration process is not easy to achieve after treatment.

Cationic Membrane Electrolysis Method
The plating solution still needs to be diluted before treatment, and the lifespan of the cationic membrane is relatively short.
Redox Alternating Electrolytic Deposition Method
A large amount of reducing agent is required to reduce hexavalent chromium to trivalent chromium, then electrolyze to remove copper and iron impurities, and finally electrolyze to oxidize trivalent chromium back to hexavalent chromium. The process is complex and energy-consuming.

Microporous Membrane Electrolysis Method
Compared to the previous three methods, the selection and lifespan of raw materials have been effectively resolved, and energy consumption is relatively low, making it a main approach for industrial applications. This method has been widely used abroad.

3. Introduction of Advanced Foreign Technology
    Since last year, Dongyun Chemical has begun technical cooperation with a German chemical company, with the German company providing technology and main materials.
    Dongyun Chemical is responsible for the research and development of chromium solution impurity removal equipment. After several months of testing, all technical indicators of the chromium solution impurity removal equipment have met design requirements.
    This technology uses microporous membranes and special waveform rectifiers. Through clever design, it not only effectively improves the electrolysis effect but also minimizes energy consumption, while being easy to operate. The relevant technology has been patented for intellectual property protection.

4.1 Comparison of Plating Solution Parameters:
     A certain hard chrome factory used 1000L of waste liquid for 13 months, and the impurity content of the plating solution was relatively high. After treatment with impurity removal equipment, the impurity content in the plating tank was significantly reduced, even exceeding our expected results. The data is as follows:

4.3 Test Piece Comparison
After the plating solution was treated to remove impurities, the impurity content decreased. Through test piece testing, the dispersion ability of the coating was improved, and the brightness range of the coating was also expanded. (1#: Original solution; 2#: Plating solution after 120 hours of electrolysis; 3#: Plating solution after 200 hours of electrolysis)

4.4 On-site Testing of Chromium Solution Impurity Removal Equipment
Testing Manufacturer: Dongyun Second Factory; Plating Tank: No. 2 Chromium Tank on Line 1;
Testing time for chromium solution impurity removal tank: 30 days;
The usage effect is as follows:

 5 Application Convenience
 

Good application effect
Excellent impurity removal effect, low energy consumption, widely used abroad.

Convenient for customer installation
Complete accessories, customers only need to make simple piping and current connections to use.

Scientific structural design
Significant for improving electroplating quality and reducing production costs.

Simple operation
Semi-automated control, easy for personnel operation, saving time and effort.