4
$\begingroup$

Questions:

  • The detailed surface treatment to turn nickel plated steel black.
  • The reaction mechanism of the process.

Methods:

  • (preferred) Anodizing, oxidizing : The only black nickel oxide is $\ce{Ni2O3}$ but I'm not sure if it's suitable for surface protection. I do not know the color or other Ni(II) or Ni(III) compound. There are nickel blackening solution for sale, but I don't know their ingredients.

  • (not preferred) Electroplating onto the existing nickel: US military have a standard to electroplate black nickel (MIL-P-18317). However this process is quite a fuss.

$\endgroup$
2

2 Answers 2

2
$\begingroup$

The article provided by Karl has answered the question with electroplating method, which is not preferred but this is the only answer I have.


  • The method is based on MIL-P-18317. The electroplating solution consists of $\ce{NiSO4, Ni(NH4)2(SO4)2, ZnSO4}$ and $\ce{NaSCN}$

  • The black nickle coating are $\ce{NiS}$ and $\ce{ZnS}$.
  • $\ce{NiS}$ and $\ce{ZnS}$ are deposited by $\ce{M^2+ + H2S -> MS + 2 H+}$.
  • $\ce{H2S}$ is generated by $\ce{SCN- + 3H+ + 2e- -> H2S + HCN}$

note: Is reducing thiocyanate a standard method to generate sulfide in electroplating ? I know soluble sulfide salts smells horrible, but it is worth the trouble ? not mentioning the cyanide byproduct, in acidic solution.


  • Metal $\ce{Ni}$ and $\ce{Zn}$ are also deposited $\ce{M(NH3)2^2+ + 2e- -> M + 2NH3}$.
  • The role of $\ce{NH4+}$ is to generate $\ce{M(NH3)2^2+}$ prior to metal deposition.
$\endgroup$
1
  • $\begingroup$ You may want to review those chemical formulas. You have nickel(I) sulfate and a double sulfate with nickel(0). ??? $\endgroup$ Aug 14, 2020 at 15:15
0
$\begingroup$

You can use PVD or CVD method. You will get a nano coating of Ni oxides. In PVD chamber you can heat Ni steel with $\ce{N2 + O2}$ or $\ce{Ar + O2}.$

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.