Trivalent chromium black passivation for chloride bath


  • Contains trivalent chromium and produces a more appealing black appearance compared to conventional agents.
  • Ideal black passivation of zinc plating in chloride bath.
  • Longer service life, lower replenishment rate and more attractive appearance are achieved compared to conventional passivation agents.
    Track record of replenishment amount being halved. (YUKEN result)
  • Does not contain silver or dyes.

Product Specifications


Appearance Dark blue strongly acidic liquid (METASU YFB-NAA)
Dark brown strongly acidic liquid (METASU YFB-NB7(A))
Dark reddish-purple strongly acidic liquid (METASU YFB-RN7(A))
Colorless transparent acidic liquid (METASU YFB-ND7)

Bath makeup conditions

Chemicals used Usage range
METASU YFB-NAA 40 – 60ml/L
METASU YFB-RN7(A) 60 – 100ml/L

Usage conditions

Item Range Remark
Process temperature 30 – 40°C
Process time 30 – 50 seconds
pH 1.8 – 2.0 Verify the pH value before usage. Use caustic soda or hydrochloric acid for adjustment if the pH value falls outside of the specified range.
◎ The pH value must be adjusted to 1.9 during bath makeup.
Agitation Yes In the case of basket processing, use vibratory agitation.
In the case of rack processing, use air agitation or vibratory agitation.

Replenish conditions

Chemicals used Replenishment reference (standard)
METASU YFB-NAA 10 – 30ml/100dm2
METASU YFB-NB7(A) 30 – 80ml/100dm2
METASU YFB-ND7 1 – 4ml/100dm2
Synthetic hydrochloric acid pH adjustment

Adjust so that the pH value is within the specified range.


Inquiry about the product

Feel free to contact us if you have any questions or matters to discuss.