The third electrode is insulated and does not receive any anode current. This electrode is freely corroding and it becomes the starting point — or reference — in eliminating corrosion. Electrodes constructed of Silver with a Silver Chloride coating (Ag/AgCl) are used exclusively with the CAPAC system.

Features
- Ag/AgCl electrodes have long life in all services
- Ag/AgCl operate in all natural waters
- Ag/AgCl have proven high stability
- CAPAC incorporates a shielded electrode
- CAPAC uses a large-area electrode
- CAPAC offers an optional cartridge electrode design
- Electrode assembly incorporates the secondary cofferdam
Benefits
- Proven 20-year installations; eliminates replacement costs
- Does not fail in brackish or fresh water like Zinc electrodes
- Stability is shown to be better than 10 mV (Zinc is 135 mV)
- Potential does not change with speed, as do exposed designs
- Potential does not change with contaminants, as do others
- Cartridge electrodes can be changed while afloat
- Reduced installation time and cost