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High
P-Ratio Parkerizing Agent DH-3250
1.
General
introduction
DH-3250 is
a high P-ratio fast parkerizing agent of the
Zinc-Nickel-Manganese 3-element system, with
a low-temperature and low-dreg character.
The agent, through its chemical effects,
forms a thin yet even and solid high P-ratio
parkerizing film, which is required by most
demanding base finishing, such as the
painting of automobile parts by cathode
electrophoresis. That parkerizing film can
remarkably improve the attachment of paint
and the resistance against erosion. The
surface after finishing will look more
refined and showy.
The
agent consists of components in 5 packets:
a)
DH-3250A(for preparing the tank)b)
AD-E(for preparing the tank)
c)
DH-3250B(for reinforcement)
d)
activator AC-1
e)
neutralizer NT-Y
2.
Technical procedure
degreasing --- cleaning
in water --- cleaning in water --- (surface
adjustment) --- parkerizing --- cleaning in
water --- cleaning in water --- cleaning in
pur water
degreasing --- cleaning in water ---
pickling in acid --- cleaning in water ---
(surface adjustment and neutralizing) ---
parkerizing --- cleaning in water ---
cleaning in pure water
degreasing and rust
removing --- cleaning in water --- cleaning
in water --- surface adjustment ---
parkerizing --- cleaning in water(hot water)
Choose one of the above
procedures and when it has been gone
through, put the work piece handled into an
oven to be
dried.
3.
Preparing the tank(1000L)
a)
Let the tank contain water up to 80% of the
total volume.
b)
Put in 55kg of DH-3250A, and stir well.
c)
Put in 6kg of AD-E, and stir well.
d)
Take 10.6kg of NT-525 and dilute it with 40L
of water, and then add them into the tank.
e)
Pour in more water to make up the total
volume 1000L.
f)
Heat the liquid to the required temperature,
and test the acidity.
g)
Add 0.50kg of activator AC-1 and stir well
before handling the work piece.
4.
Treatment conditions
General acidity --- 22-25Pt free
acidity --- 0.6-1.2Pt
Activator density --- 2-3Pt
temperature --- 40-45°C
Time duration --- 2-5 minutes
5.
Supplement and adjustment
As
the density keeps changing during the
treatment, density tests must be made at
regular intervals to maintain it within the
required range. Adding every 2.0kg of
DH-3250B will increase the general acidity
by 1pt. But if overflow has caused loss of
the liquid, extra water and DH-3250A should
be added. Every 2.3kg of DH-3250A can
increase the general acidity by 1pt.
Free acidity may be
lowered by neutralizer --- On condition that
only small pieces or no pieces are being
treated and the parkerizing liquid is as hot
as over 45°C, or that the DH-3250B has been
put in too much, then free acidity will go
up over 1.2pt. In that case, neutralizer is
needed for regulating the liquid. Every 200g
of neutralizer can lower the free acidity by
1pt.
Activator ---
Activator in the liquid is consuming even
while no work pieces are being treated. So
its density should be tested in the process
of treatment and extra activator be added to
maintain the required density. Every 150g of
activator can increase the acidity by 1pt.
6.
Testing methods
General acidity --- Transfer 10ml of the
liquid with a suction pipet into a 250ml
beaker and add 5 or 6 drops of
phenolphthalein. Titrate with NaOH(0.1N).
When the color turns from colorless to pink,
it is the end of the titration. The number
of ml used is the value of general acidity.
Free acidity ---
Transfer 10ml of the liquid with a suction
pipet into a 250ml beaker and add 4 or 5
drops of bromophenol blue indicator. Titrate
with NaOH(0.1N). When the color turns from
yellow to blue or purple, it is the end of
the titration. The number of ml used is the
value of general acidity.
Density of activator
--- Fill a fermentation tube with the
treating liquid. Add 2-5g of sulphanilamide.
Block the tube, turn it upside down and
shake it vertically. Then let it stand still
for 2 minutes. The volume of the gas
produced as indicated by the scales will be
the density of the activator. One scale
means one pt.
7.
Materials of the apparatuses
The
parkerizing tank should be made of stainless
steel or carbon steel. The heat exchanger,
the sprayer nozzle, the piping and the pump
should be made of stainless steel.
8.
Equipment maintenance
The
best way to rid the tank of deposits is to
pump the whole lot of the liquid into a
deposit tower or deposit pool, and then
return the clean liquid to the parkerizing
tank. |
