Impurities in the plating solution include inorganic impurities and organic impurities. Inorganic impurities are mainly metal ions such as copper, iron, aluminum, silicon, zinc, chromium, and nitrate ions, phosphate ions, etc.; organic impurities include bright additives and cathode electrolysis products, Various types of greases, etc. When these impurities accumulate to a certain concentration in the plating solution, they will have a serious impact on the quality of the plating layer. Therefore, the concentration of these impurities in the plating solution should be strictly controlled during the electroplating process. Measures should be taken to remove impurities that exceed the concentration range from the plating solution. Medium clear.
organic impurities
When the plating solution is contaminated by organic impurities, the coating will often darken, produce pitting, streaks, pinholes, increase brittleness, etc. Excessive additives will cause stripes, increased brittleness, and darkening of the coating in low current areas. Excessive amounts of some additives can also passivate the coating, causing difficulties in subsequent chromium plating. The decomposition products of additives cause the brittleness of the coating to increase and affect the brightness and flatness of the coating. Grease or improper wetting agents can cause the coating to appear orange peel-like.
Organic impurities that can be adsorbed by activated carbon, such as greases and most wetting agents, can usually be treated directly with activated carbon. If organic impurities need to be oxidized, potassium permanganate or hydrogen peroxide can be added to the plating solution. The steps for oxidizing organic impurities and treating them with potassium permanganate are as follows.
① Use sulfuric acid or hydrochloric acid to adjust the pH value to 1.5~2.5, and raise the temperature to about 40°C; weigh the required amount of potassium permanganate at 0.25g/L and dissolve it in pure water.
② Add the potassium permanganate solution into the plating solution with constant stirring, and let it sit for about 20 minutes; if excess potassium permanganate is found in the oxidized plating solution, a small amount of hydrogen peroxide can be used to reduce the potassium permanganate.
③Adjust the pH value to about 5 with nickel carbonate or barium carbonate, and continue stirring for about 150 minutes.
④Add activated carbon at 2~5g/L, stir evenly, let it sit for several hours and then filter.
⑤ Analyze and adjust the plating solution, and re-add all additives according to process requirements. It can be used for production after passing the trial plating.
