MX-Zn-D-31H Zinc electroplatingtrivalent
chromium black passivation
Features:
1. Newly-designed environment-friendly zinc electroplating black passivation, no more
use of metal salt, like silver, iron and nickel, as blackening compositions.
2.no toxic metals,
like silver, and hexavalent chromium
in passivation solution.
3. Easy to operate, stable
solution, brightly black-colored.
4. No use of iron salt to blackening
the plating, good corrosion resistance, could reach more than 72 hours in NSS
(neutral salt spray) test;
5. Applicable to all
kinds of zinc electroplating.
Process and operation
condition
Processes:
zinc electroplating—tertiary washing—0.2-0.5% nitric
acid’s bright—washing— trivalent chromium black
passivation—washing—sealing—washing—dry—lacquer (acidic zinc
electroplating depends on situation)—dry
Passivation operation condition:
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Scope
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Remarks
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MX-Zn-D-31HA(ml/L)
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50(50-80)
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Adjust PH value by sodiun hydroxide or nitric acid.
If get bigger surface of work pieces, improve PH
value to2.6-2.8 and lengthen passivation time to get evenly-color.
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MX-Zn-D-31HB(ml/L)
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50(40-60)
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PH
value
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2.4(2.2—2.8)
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Temperature(℃)
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25(15-35)
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Time(s）
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60(50-100)
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filtering
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Air
mixing
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Sealing operation condition:
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Scope
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Recommended value
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MX-Zn-D-31HC(ml/L)
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60—120
|
100
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PH value
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3.8—4.5
|
4.0
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Temperature(℃)
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40-60
|
50
|
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Time(s)
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5-15
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10
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Mixing
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slight mixing
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Maintenance:
Production replenishment of MX-Zn-D-31H A and MX-Zn-D-31H
B in proportion of 1:1.
MX-Zn-D-31H
replenishment is in proportion to the treatment area
Add 1L MX-Zn-D-31H A and MX-Zn-D-31H B every time
dealing with 3000dm2 of zinc plating pieces, Add 1L MX-Zn-D-31H C every time
dealing with 5000-10000dm2 of zinc plating pieces; but there is discrepancy
according to product requirement and input;
When bath works for 6-8 hours for consecutive 5
days, decomposition and dissolved impurities would exceed. In this case,
part of bath could be changed, or be passivated half of time with old bath and
the other with new bath, in other words 2 times passivation to reduce usage.
The tolerance of metal impurities: zinc 10g/L, iron
30mg/L, copper 5 mg/L.
