galvanostats

A galvanostat is an instrument designed to control and maintain a constant electrical current through an electrochemical cell. In electrochemical research and industry, a galvanostat provides a controlled current at the working electrode by adjusting the potential difference between the working and counter electrodes. Unlike a potentiostat, which regulates the electrode potential, a galvanostat uses feedback to keep the current at a user-set value over a specified period. Modern galvanostats are often integrated into electrochemical workstations and can operate in constant-current or programmable current-waveform modes.

Operation relies on a current-sensing element, typically a low-value shunt resistor, and a feedback amplifier that modulates the applied voltage to maintain the chosen current. The device can source or sink current in either direction and reports the actual current and the resulting electrode potential. A compliance voltage, or limit, sets the maximum voltage the instrument will apply to sustain the current against solution resistance and polarization effects.

A three-electrode cell is common, with a working electrode, counter electrode, and reference electrode. The galvanostat drives current between the working and counter electrodes while the reference electrode monitors the potential at the working electrode. The instrument can run in steady constant-current mode or with time-programmed current steps, ramps, or pulsed sequences.

Applications include electrodeposition and electroplating, charge/discharge testing of batteries and supercapacitors, galvanic corrosion studies, and electrolysis. The ability to fix current allows precise control of the total charge passed (Q = I t) and hence the amount of material deposited, consumed, or transformed. Limitations arise from solution conductivity, electrode geometry, polarization, and mass-transport limits, which can cause deviations from ideal constant-current behavior.

Compared with a potentiostat, which fixes potential, the galvanostat emphasizes current control. Some instruments offer both modes or combine current and potential control in a single device, allowing seamless switching between galvanostatic and potentiostatic operation.