HIGH SPEED BRASS PROCESS UNIBRASS 720
PHYSICAL PROPERTIES:UNIBRASS 721:Green Liquid.
UNIBRASS 722:Brown Liquid.
UNIBRASS 723:Clear Liquid.
DESCRIPTION:
Brass is an alloy of copper and zinc and is the most widely used alloy electroplated.
The largest amount of brass plating is for decorative use. For bright decorative work,
most is done by flash plating brass over bright nickel or other suitable bright plate.
The brass alloy most often plated is a yellow color and contains 70 to 80% copper with the balance zinc. This is a ductile, stable alloy with only about one shade of color variation over the entire range.
SPECIFIC USE:
The High Speed Brass Process UNIBRASS 720 produces brilliant brass deposits with good throwing and covering properties.
The color of deposits may be varied by adjusting the concentration of the Stabilizer
UNIBRASS 723.
EQUIPMENT:If possible, plating tanks should be plastic lined to avoid stray currents.
BATH MAKE-UP PER 1.000 l
Make-up Salt UNIBRASS 720-70 kg
Zn(CN)²-62,5 kg (Copper Correction Salt)
CuCN-22 kg (Zinc Correction Salt)
NaCN-85 - 100 kg
Brightener UNIBRASS 721-20 l
Brightener UNIBRASS 722-15 l
Stabilizer UNIBRASS 723-depending on desired color.
Dissolve Zinc-, Copper- and Sodiumcyanide together in one third of the desired volume of water. Attention solution heats up !!
Dissolve Make-up Salt UNIBRASS 720 in a separate tank.
Now mix both solutions together and fill up with water to final volume, adjust the
temperature and add the Brighteners UNIBRASS 721 and UNIBRASS 722.
And, if required, Stabilizer UNIBRASS 723. Stirr well !!
OPERATING CONDITIONS:
Current Density0 - 3 A/dm²
Temperature40 - 50° C
Optimum Temperature45° C
pH-Value9.5 - 11
Current Efficiency40 - 50 %
Anodes (%Cu to %Zn)70/30 or 60/40
(or Stainless Steel)
CONSUMPTION PER 10.000 Ah:
Brightener UNIBRASS 721-0,8 - 1,2 l
Brightener UNIBRASS 722-0,8 - 1,2 l
Stabilizer UNIBRASS 723-0,0 - 1,0 l depending on desired color
ANALYSIS:
Copper-12 - 17 g/l
Zinc-32 - 38 g/l
Free cyanide-45 - 55 g/l
Total cyanide-80 - 90 g/l
ANODES:
Anodes should be approximately of the same composition as the alloy being plated.
For general yellow brass plating, 70% Cu/ 30% Zn anodes are recommended.
Cast or rolled anodes are satisfactory.
Common shapes are balls, slugs or flat top shapes which fill fit the anode baskets used. Steel baskets are subject to corrosion under some conditions, putting iron into solution
as ferrocyanides. The ferrocyanides precipitates with the zinc in the solution, giving a white to grey precipitate. This should be filtered out or otherwise removed.
Purity of the anodes is important. Lead is a common impurity and must be kept below 0.02%. Lead in very low concentrations causes red plate in recesses. Tin should also be kept below 0.03%. Other metallic impurities are not as critical nor as apt to be found.
GENERAL INFORMATION:
No special cleaning or preparation is necessary on most base metals for brass plating. Equipment required is that conventionally used for all cyanide plating solutions.
Properly operated, the brass plating solution will maintain color and alloy over a wide range of current densities. When the range of uniform color is narrow, it is usually because the solution is out of balance. Additions must be made to restore balance. If the balance is correct, the cause is impurities in the solution. Organic impurities such as emulsified dirts can cause brown or off-color dull plates.
Filtration, especially through activated carbon, will remove these impurities. Metallic impurities may be plated out at low current densities. Obviously, if the anodes are impure, dummy plating will not remove impurities unless the impure anodes are replaced by anodes of acceptable composition.
SPECIAL INFORMATION:
While conventional brass plating fills most of the needs, higher speed solutions are often necessary where heavier thicknesses are required for special uses.
The higher speed is due to the greater efficiency and higher current densities possible.
At the lower end of the temperature range, color has to be maintained by adding Stabilizer UNIBRASS 723. Additions may be made as offten as hourly.
To maintain an uniform color and to give a wide plating range, it is important to keep both Copper and Zinc, at their respective levels. If the brass deposit is too light, Zinc Correction Salt (CuCN) should be added.
If the deposit is too red, Copper Correction Salt (Zn(CN)²) should be added.
To dissolve both salts completely it is necessary to mix them with Sodiumcyanide in a separate tank and then add them to the bath.
CuCN in a ratio of 1 : 1.4 and Zn(CN)2 in a ratio of 1 : 1.
To increase the quality of deposit over a wide plating range it is important to use our Brighteners UNIBRASS 721 and UNIBRASS 722.
These solutions are suitable for both, rack and barrel plating.
Barrel solutions are generally operated at slightly lower temperatures than still tanks.
To produce the higher copper(gold colored) alloys, the high alkali high speed brass
may be used, by using potassium cyanide rather than sodium cyanide and operating at lower temperatures.
Higher copper alloys such as so called red brass alloy or architectural bronze
(85%Cu to 15%Zn or 90%Cu to 10%Zn) can be plated.
The major change is to operate with a higher cyanide to zinc ratio. The solutions have lower efficiency than conventional yellow brass. Partially to compensate for this, they are operated at temperatures of 33 to 52° C and with higher copper content.
SAFETY PRECAUTIONS:see Material Safety Data Sheets
GUARANTEE:
Above instructions and recommendations are the result of intensive testing and shop experiences. They are for your information, only.
Our guarantee extends to the continuous quality of our products as they leave our factory and not to their useage in the field, which is a factor beyond the control of a supplier.
V.KunzRev 1.118.10.20021/4