Sample Masking; Electrode Connections: Corrosion - Gamry Instruments ParaCell Operator's Manual

Electrode Connections: CorrosionSample Masking
The ParaCell is designed for use with flat samples that are conductive through the sample—from the solution
interface to the back wall, in contact with the leveling sample bracket. When this is the case, the banana jacks
in the brackets can be used for electrical connection to the potentiostat. The colors are coded for Gamry
potentiostats, with the working side having green and blue banana jacks, and counter side having red and
orange, but the coloring is only a visual aid; the cell can be connected in other manners.
You may use flat samples that are not conductive through to the back side, but you must find an alternate
method for electrical connection.

Sample Masking

While the opening sealed with the included O-ring does define an electroactive area, in many cases we advise
to mask off a somewhat smaller area on the sample surface. When sealed to a flat sample with an O-ring or
gasket, a crevice region is formed. This area will have unusually high activity for corrosion and also affect
physical electrochemistry experiments.
Masking minimizes crevice effects that can skew results. Masking an electrode can be done in different ways.
PortHole sample masks are available from Gamry Instruments to provide a fixed, known area. It is not necessary
to mask the counter electrode in three-electrode potentiostatic/galvanostatic experiments. If you are doing
galvanic corrosion, then both metal samples should be masked in the same way. When masking, make sure the
revealed area is centered in the hole when mounting the electrode.

Electrode Connections: Corrosion

If you are using your ParaCell with a Gamry Instruments potentiostat, make the following connections to the
electrodes:
The Reference Electrode lead plugs into the white pin jack on the cell cable.
The green, blue, red and orange leads are plugged into their respective colored jacks (when using through-
conductive samples set up with the working electrode on the green/blue side). For most experiments, the
counter sense lead (orange) is not necessary, but it is nice to have some place to put it. Some potentiostats do
not have a separate work sense lead. While this does give less-accurate voltage measurement and control, it
does not affect the use of this cell. You just have only one lead to attach to the working electrode side.
Make sure that the black lead on the cell cable cannot touch any other cell connection, or other metal of the
cell body/sample(s). Connecting this lead to a source of earth ground, such as a water pipe, may reduce noise in
your experimental results. If you are measuring very small currents, a metal enclosure completely surrounding
your cell may further reduce noise. In this case, connect the shield, known as a Faraday cage, to the
potentiostat's ground lead and perhaps also to earth ground. The ParaCell works with Gamry's VistaShield™
Faraday cage, which allows you to see the cell without breaking the shielding.
Always double-check your cell connections. Even an experienced experimenter will
occasionally leave one of the cell cable leads lying on the desktop.
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