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BRASSO
SHINE - BRASS PLATING PROCESS-730
This
is a Brass Plating Process used as a decorative
finish on
Ferrous Metals,
Tin-Plate and upon Zinc base Alloy. On steel
it is usual
to apply an initial deposit of bright nickel or
bright copper from a leveling type of solution and then
to brass plate for
a short
period in the 730 process, so that a
bright brass finish is
obtained. Tarnishing of brass deposits can be
avoided by either lacquering or by the use of antitarnish
treatment with 1102
solution. The process solution can be used either
warm or
cold, but speedier deposition and brighter results are
obtainable with warm solution.
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Bath make up
and operating condition :
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Vat
|
Barrel
|
|
Brasso
shine salt-731 |
100
gm/lit
|
150 gm/lit. |
|
Liquor
ammonia (sp.gr.0.90) |
10 ml/lit. |
20-25
ml/lit.
|
|
Brasso
shine brightner-732
|
4 ml/lit.
|
6 ml/lit.
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Temperature
|
25-45* c
|
25-40* c
|
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Density
|
6-8*
be |
10-12*
be
|
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Cathode
c.d.
|
0.3-0.6
amp/sq.dm
|
0.2-0.3
amp/sq.dm.
|
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Anode
c.d.
|
0.2-0.3
amp/sq.dm
|
0.1-0.2
amp/sq.dm.
|
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Voltage
|
2.5-4.0
volts
|
6.0-9.0 volts
|
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Ph
value
|
10.5 - 11.0
|
11.0 - 11.5
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Copper
metal
|
8.0-10.0 gm/lit.
|
12.0-14.0 gm/lit.
|
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Zinc
metal
|
2.5-3.5 gm/lit.
|
3.5-4.5 gm/lit.
|
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Free
sodium cyanide |
6.0-8.0 gm/lit. |
9.0-12.0 gm/lit. |
Equipments :
Mild
steel tank and heater can be used. A plastic container
may also be used. To maintain consistent brass plating
quality it is
important to
control temperature and current
accurately. The
rectifier and all electrical connections should be clean and
well maintained.
Anodes :
High
purity lead free brass anodes of 65 % copper and 35 %
zinc composition are
used. Anode area should
be as
large as possible to minimise the formation of slimes and to control
polarisation.
Solution
make up :
Fill
the clean
tank with
2/3 full of
deionized water.
Add required quantity of salt-731 slowly with vigorous
stirring. Stir further to get dissolve completely. Make up the
level with water. Add required
quantity of liquor ammonia and
brightner-732 with
stirring and use the bath.
Bath
maintenance :
Close
control of
temperature is necessary to
maintain color
and cathode efficiency
of the deposit. An increase in temperature of
the bath will
increase the copper content of the deposit and
it should
operate at preferable temperature to get rich brass color. The
brass deposit is
normally a rich golden colour, but any shade from a
pale yellow to
a reddish gold may be obtained from the same
solution by
varying temperature and current density. The decorative type
of bath
should be worked at very low voltage they will generally deposit
brass rich in
colour and
of reddish appearance but if
operated at
high voltage they
will yield plating of high zinc content that
is either very pale or bronze in color.
Regular addition of
brightner-732 is made at 250-300 ml per 1000 amp.- hour basis.
Ph should be maintained between 10.50 to
11.5 by adding
liquor ammonia
or sodium
bicarbonate. Maintenance of
free sodium
cyanide is also important low concentration of sodium
cyanide leads
to blistering, and off colour, high concentration of
cyanide will lead to low cathode efficiency and skip plating. Concentration
of copper
and zinc content
should be kept within the specified
limits. Liquor
ammonia is
useful for controlling the colour of the brass deposits
and anode corrosion. It is therefore suggested to add 0.25-0.5 ml/lit of ammonia at regular intervals.
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