Additive for Chrome Plating
1. Properties
1. Wide technique range and good covering ability. The throwing power can increase by 30~60%, the current efficiency is up to 22~24%, non-corrosion at the low current area.
2, High tolerance to impurities.
3. Low content of chromic acid, it is 40% of conventional plating solution. Can reduce the content of chromic acid in waste water, easy to handle.
4. The technique is stable, easy to maintain.
2. Technical Formulation and Operating Condition
| Chromic acid (CrO3) | 150~250g/L |
| Sulfuric acid (H2SO4) | 0.75~1.88g/L |
| CHROME 31 | 5~9ml/L |
| Cr3+ | 0.5-3g/L |
| Temperature | 18~50℃ |
| DK | 15~20 A/dm2 |
| Anode | Lead-Tin alloy plate (Tin content is 8~15%) |
| Gravity | 19~23°Be |
3. Using Method
1. Make-up the new bath:
Prepare the new bath according to conventional chrome plating technique process, after that, add CHROME 31 into the solution, heat to 40 ~50℃ and stir the solution to make it completely dissolve, then try plating.
If the plating tank is a little bigger, make it activated by electrolyzing for 1-2 hours before trying plating. Pay more attention to the sulfuric acid quantity when add it into the bath, because some Chromic acid(CrO3) contains higher SO4 2- content itself.
2. The conversion of the old plating bath:
To old plating solution, sample it and analyse the SO42- content in old plating solution. According to the analyse result, use BaCO3 to deposi the redundant SO42- , adjusting the plating solution to normal level.If there is much deposit in the bath, and not be filtered for long time, can add excess BaCO3 to make bath clean, fully stir, filter or stand the solution for more than 12 hours, then take out the clear solution from the top level, adjust CrO3 and H2SO4 to the routine, then add CHROME 31 additive according to the above methods.
3. The daily replenishment of CHROME 31:
CHROME 31 can improve cathode current efficiency , and make throwing power better. Adding 1Kg chromic acid requires to add 30 ml CHROME 31. The replenishment quantity also can be calculated by the Hull tank test , or add it as 10-20ml/KAh.
4. If using CHROME 31 additive instead of chrome plating additive from other supplier, firstly, add measured BaCO3 and fully stir, then stand the solution for more than 12 hours, then take out the clear solution from the top level, adjust H2SO4 and CrO3 content , then add CHROME 31 1/3 ~1/2 amount of the make-up bath(If add CHROME 31 6ml/L when make the new bath, now add 2-3ml/L).
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