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Nickel electroplating

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Nickel electroplating is a technique of electroplating a thin layer of nickel onto a metal object. The nickel layer can be decorative, provide corrosion resistance, wear resistance, or used to buildup worn or undersized parts for salvage purposes.[1]


Overview

Nickel electroplating is a process of depositing nickel on a metal part. Parts to be plated must be clean and free dirt, corrosion, and defects before plating can begin.[2] To clean and protect the part during the plating process a combination of heat treating, cleaning, masking, pickling, and etching may be used.[1] Once the piece has been prepared it is immersed into an electrolyte solution and is used as the cathode. The nickel anode is dissolved into the electrolyte in form of nickel ions. The ions travel through the solution and deposit on the cathode.[3]

Types and Chemestry

Watts

Watts nickel plating baths can deposited both bright and semi-bright nickel. Bright nickel is typically used for decretive proposes and corrosion protection. Semi-bright deposits are used for engineering nickel where a high luster is not desired.[4][5]

Chemical Name Formular Bright[4] Semi-bright[4]
Nickel sulphate NiSO4·6H2O 20-40 oz/gal 30-40 oz/gal
Nickel chloride NiCl2·6H2O 8-20 oz/gal 4-6 oz/gal
Boric acid B(OH)3 5-7 oz/gal 5-7 oz/gal

Nickel sulfamate

Sulfamate nickel plating is used for many engineering applications. It is deposited for for dimensional corrections, abrasion and wear resistance, and corrosion protection. It is also used as an undercoat for chromium.[6]

Chemical Name Formular Bath Consentration [3]
Nickel sulphamate Ni(SO3N2)2 40-60 oz/gal
Nickel chloride NiCl2·6H2O 0-4 oz/gal
Boric acid B(OH)3 4-6 oz/gal

All-Chloride

All-Chloride solutions alow for the deposition of thick nickel coatings. They do this becouse they run at low voltages. However, the dosposion has high internal stresses. [3]

Chemical Name Formular Bath Consentration [3]
Nickel chloride NiCl2·6H2O 30-40 oz/gal
Boric acid B(OH)3 4-4.7 oz/gal

Sulfate-Chloride

A Sulphate-Chloride bath operates at lower voltages than a Watts bath and provide a higher rate of deposition. Although internal stresses are higher than the Watts bath they are lower than that of a all-chlorine bath. [3]


Chemical Name Formular Bath Consentration[3]
Nickel sulphate NiSO4·6H2O 20-30 oz/gal
Nickel chloride NiCl2·6H2O 20-30 oz/gal
Boric acid B(OH)3 4-6 oz/gal

All-Sulfate

An all-sulfate solution is used for electrodepositing nickel where the anodes are insoluble. For example, plating the insides of steel pipes and fittings may require an anode. [5]

Chemical Name Formular Bath Consentration[3]
Nickel sulphate NiSO4·6H2O 30-53 oz/gal
Boric acid B(OH)3 4-6 oz/gal

Hard nickel

A hard nickel solution is used when a high tensile strength and hardness deposite is required. [3]

Chemical Name Formular Bath Consentration[3]
Nickel sulphate NiSO4·6H2O 24 oz/gal
Ammonium chloride NH4Cl3 3.3 oz/gal
Boric acid B(OH)3 4 oz/gal

Black nickel

Black nickel plating is a typically plated on brass, bronze, or steel in order to produce a non-reflective surface.[7] This type of plating is used for decretive purposes and does not offer much protective value.[1]

Chemical Name Formular Bath Consentration[7]
Nickel Ammonium Sulphate NiSO4·(NH4)2SO4·6H2O 8 oz/gal
Zinc Sulphate ZnSO4 1.0 oz/gal
Sodium Thiocyanate NaCNS 2 oz/gal

Applications

Decorative bright nickel is used in a wide range of applications. It offers a high luster finish, corrosion protection, and wear resistance. In the automotive industry bright nickel can be found on bumpers, rims, exhaust pipes and trim. It is also used for bright work on bicycles and motorcycles. Other applications include hand tools and household items such as lighting and plumbing fixtures, wire racks, and appliances.[4]

Engineering nickel is used where brightness is not desired. Non decorative applications provide wear and corrosion protection as well as low stress build ups for dimensional recovery. [4]

See also

Electroless nickel plating
Electroplating

References

  1. ^ a b c QQ-N-290A
  2. ^ MIL-P-27418
  3. ^ a b c d e f g h i http://www.substech.com/dokuwiki/doku.php?id=nickel_electroplating
  4. ^ a b c d e http://www.pfonline.com/articles/pfd0015.html
  5. ^ a b NickelElectroplating.pdf
  6. ^ http://www.balesmold.com/sulfamate.htm
  7. ^ a b MIL-P-18317
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