Metal finishing Q&As since 1989

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Black oxide on electroless nickel plate

Is it ok to apply black oxide over the top of electroless nickel plate (AMS2404, class 2)?

Susan Yip
engineer - Phoenix, Arizona
July 9, 2010

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July 9, 2010

Hi, Susan. I doubt that it's even possible. Black oxide is not an electroplating. Rather it is a conversion coating. It's the reaction product of steel exposed to the nitrates and other oxidizing compounds in the bath. If you don't have steel on the surface you can't convert it to black oxide.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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July 18, 2010

Hi Susan,

The electroless Ni-P coating can be blackened by an oxidation treatment.

Is it for solar collector?

After electroless plating, the plated samples can be etched using four different methods:

Method 1 - immersion in a solution containing 6.0 M sulfuric acid (Aldrich) and 4.0 M nitric acid (Aldrich) (60 ≥aC, 20 s).

Method 2 - immersion in 9.0 M nitric acid (40 ≥aC, 40 s).

Method 3 - immersion in a solution containing 5.5 M sulfuric acid and 4.1 M Sodium Nitrate [affil links] (Aldrich) (50 ≥aC, 40 s)

Method 4 - Method 1 followed by rinsing and drying of the artifact followed by Method 2.

The blackening is a function of the phosphorus content of the deposit and morphological features of the coating

Ref: Richard Brown et al., J. Mater. Chem., 2002, 12, 2749…V2754

T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note Nov. 2017: The good doctor has a fascinating blog at https://advancementinscience.wordpress.com)