Trivalent Chromium Black Passivator for Zinc Plating(MX-Zn-D-31H)

Newly-designed environment-friendly zinc electroplating black passivation, no more use of metal salt, like silver, iron and nickel, as blackening compositions. No toxic metals, like silver, and hexavalent chromium in passivation solution. Easy to operate, stable solution, brightly black-colored. No use of iron salt to blackening the plating, good corrosion resistance, could reach more than 72 hours in NSS (neutral salt spray) test. Applicable to all kinds of zinc electroplating.



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:

 

Scope

Remarks

MX-Zn-D-31HA(ml/L)

50(50-80)

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.

 

MX-Zn-D-31HB(ml/L)

50(40-60)

PH value

2.4(2.2—2.8)

Temperature(℃)

25(15-35)

Time(s)

60(50-100)

filtering

Air mixing

 

Sealing operation condition:

 

Scope

Recommended value

MX-Zn-D-31HC(ml/L)

60—120

100

PH value

3.8—4.5

4.0

Temperature(℃)

40-60

50

Time(s)

5-15

10

Mixing

slight mixing

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.


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