Palm's Instruments Division
ENStat II Stainless Steel Passivation
ENstat II is an electrochemical system for continuously
passivating the stainless steel components used in electroless
plating baths. Its use helps prevent plate-out and avoids stripping
the tank with nitric acid on a daily basis. The use of this system
thus minimizes disposal of spent nitric acid solutions and the
cost of their waste treatment.
The ENstat II is based
upon the electrochemical technique of anodic protection, which
has been used for many years to prevent corrosion of equipment
in the chemical industries. Simply, anodic protection produces
a passive film on the stainless steel by discharging a small
impressed current from it at a carefully controlled potential.
This film is very similar to that produced by nitric acid passivation
and prevents deposition of electroless nickel, while also avoiding
corrosion of the stainless steel.
The difference between this technique
and the reverse current passivation method used in the past,
is that with depleting the potential of the stainless steel is
not controlled. Instead a large current is discharged from the
metal to keep it from plating. This discharge, however, also
causes the stainless steel to corrode and become etched, especially
at the welds. With Enstat II only the amount of current
needed to prevent plate-out is used to maintain the potential
of the metal within a desired range. In addition, at the proper
potential, most current is discharged through oxygen evolution
rather than by metal dissolution.
Not only will the Enstat II
protect the plating tank, but it will also reduce plate-out in
the stainless steel pumps and heat exchangers electrically connected
to it. Because protection is not dependent upon current flow,
passivation does not change significantly with distance.
Hundreds of anodic protection
systems have been installed on electroless plating tanks in Europe,
some for more than twenty years. These installations have been
very successful and have allowed the plating solutions to remain
in the same tank for as long as one month without nitric acid
The ENstat II is a microprocessor
controlled potentiostat, specifically designed to protect stainless
steel equipment in electroless plating solutions. Its operating
program was especially designed to assure stable, trouble free
operation. In addition, the instrument automatically tests the
condition of the tank and instrument to ensure that the system
is operating properly. Most of the common errors or faults observed
during field and laboratory tests were included in the program.
The program includes default values which are adequate for most
baths and tanks. However, if a custom set is required a new set
up for operation may be done by following the plain English display
instructions. To prevent unauthorized access a hardware key will
lock out this mode.
The unit can provide a sustained
output of 10 amperes, and thus is adequate for even the largest
electroless plating tanks.
ENstat II is supplied in a NEMA 4 enclosure suitable
for plating environments. Includes insulated cables with quick
disconnect couplings for the anode and cathode connections. The
reference electrode also includes a shielded cable with quick
Reference voltage, open circuit,
short circuit, and bath temperature shut down.
0-1.20 volts Reference, 0-3.00 volts
output, 0-10 amps current.
Short circuit, open circuit, overload,
low bath temperature.
110/220 vac @ 20 Amps
4 x 20 backlite super twist LCD