Nickel

SEMI BRIGHT

MAR NICKEL PRO 400 SB is a specially formulated semi-bright process which provides a sulfur-free, leveling deposit with excellent mechanical properties and with outstanding corrosion resistance when used as an undercoat in a duplex nickel system.

The MAR NICKEL PRO 400 SB process has been developed expressly for use as the semi-bright component of duplex plating. The bright top plating recommended MAR NICKEL PRO 310. This process has all of the desirable properties needed as a companion coating to the MAR NICKEL PRO 400 SB process. The recommended ratio of deposit thicknesses for optimum results is 65 to 75 percent of MAR NICKEL PRO 400 SB semi-bright nickel and 35 to 25 percent of the bright MAR NICKEL PRO 310 process.

MAR NICKEL PRO 400 SB Semi-Bright Nickel Process is normally maintained with one addition agent and operates effectively over a wide solution composition range. This process is ideal for all high volume production applications where simplicity of operation and control is required.

OPERATING CONDITIONS

Total Nickel 75 g/l
Temperature 45 – 60 °C
Current Density 2 – 10 A/dm2
pH 3.8 – 4.5
Agitation Mechanical
SOLUTION PREPARATION

The solution should be made up in a storage tank which has been thoroughly cleaned. The tank sides and bottom should be scrubbed with a wetting agent and hot water. Then thoroughly rinse with DI water. The lining of the tank, filters, etc., should be leached with a 0.5% by volume solution of sulfuric acid heated to 60°C (140°F), containing 400 WA-SB, 0.1% by volume. This leaching should continue overnight. Sulfo-oxygen compounds present in most full-bright nickel solutions must be leached out.

  1. Fill the storage tank two-thirds full of water and heat to 63°C (145°F).
  2. Fill the storage tank two-thirds full of water and heat to 63°C (145°F).
  3. Dissolve the necessary nickel sulfate and nickel chloride.
  4. When these constituents have dissolved, raise the pH to about 5.0 electrometric. This may be accomplished by making a thin slurry of nickel carbonate in hot water and adding it to the fresh nickel solution with vigorous stirring.
  5. Add 0.25% by volume 30% hydrogen peroxide. The peroxide should be diluted 1:10 with water before adding.
  6. Add activated carbon 2.5 g/L of solution. Stir intermittently for a few hours, then allow to settle overnight.
  7. Filter this solution into the plating tank which has been cleaned in the same manner as previously outlined for the storage tank.
  8. Clean the filter; repack the filter aid (diatomaceous earth) and activated carbon, 0.3 g/L.
  9. Add the necessary boric acid to the plating solution.
  10. Add the necessary amount of MAR Pro 400C-SB and adjust the pH to 3.5 to 4.0 electrometric with sulfuric acid (C.P. or Technical Grade).
  11. Add the required charge of MAR Pro 200 AX-SB.
  12. Add the necessary MAR Pro 400WA-SB.
  13. Electrolyze at low current density, 0.5 A/dm2, using corrugated dummy cathodes. Continue the electrolysis for approximately 12 hours or until recesses in new corrugated cathodes are light in color.
EFFECTS OF CONSTITUENTS

NICKEL SULFATE

This salt furnishes nickel ions to the solution. The nickel metal concentration of the bath as derived from nickel sulfate and nickel chloride should be approximately 75 g/L. The nickel concentration is not critical but it should be maintained within the limits of 60 to 90 g/L. In general, the higher metal concentration should be used where higher current densities are desired.

NICKEL CHLORIDE

The principal function of this salt is to promote satisfactory anode corrosion. For economical operation, the chloride content, calculated as nickel chloride, should be maintained between 38 and 45 g/L. Increase of the nickel chloride content above 45 g/L adversely affects stress and ductility.

BORIC ACID

This constituent exerts a buffing action in the cathode film. Concentration of the boric acid should be maintained between 38 to 45 g/L.

NICKEL PRO 400 C-SB

This compound functions as a sulfur-free carrier brightener, i.e., it reduces stress, improves ductility and increases the uniformity of the deposit obtained in the presence of the leveling agent 400AX-SB. The 400C-SB content should be maintained between 0.5 and 1.0% BV. Below 0.4% BV the operation of the bath is somewhat more critical while above 1.0% by vol. consumption of 400AX-SB is greater. Consequently, the 400C-SB content should be maintained at approximately 0.75% BV.

Consumption rate is about 4,000 A-h per1 litre.

NICKEL PRO 400 AX-SB

The 400AX-SB is a highly efficient leveling agent which also provides a semi-bright deposit over a wide current density range. Under normal operating conditions the concentration of 400AX-SB should be maintained at 0.16% BV by small additions several times per shift or by continuous addition to the bath on the basis of consumption of approximately 4,000 A-h/Liter.

Increase of 400AX-SB above recommended values increases the brightness and leveling and an excess produces bright, brittle and stressed deposits. The amount of 400AX-SB required to produce maximum leveling while maintaining excellent mechanical properties of the deposit will increase:

  1. By increasing current density
  2. Increase the 400C-SB
  3. By decrease of temperature
  4. By a decrease in pH
  5. By a decrease in agitation

As a general rule it is desirable to maintain the NICKEL PRO 400AX-SB concentration such that deposits in recessed areas are not fully bright.

When the 400AX-SB is excessive as indicated by fully bright low current density areas or stress cracking in extreme cases, the situation can generally be remedied by one or more of the following steps:

  1. Reduce the temperature 45°C minimum.
  2. Cautiously lower the pH. As the pH is decreased the current efficiency will drop somewhat, the leveling will decrease and the low current density coverage will be reduced.
  3. Reduce the degree of agitation. This step can be very helpful if high current density is not a problem.
  4. Increase the average current density. In some cases this will reduce or eliminate low current density difficulties without creating a high current density problem.
  5. If time is available, the 400AX-SB concentration can be reduced by dummying.

NICKEL PRO 400 WA-SB

This surfactant is recommended because of controlled foaming characteristics.

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