Cooling systems combine water, oxygen, heat and mixed metallurgy—all of which can support corrosion if chemistry is not controlled. The goal of a treatment program is not to eliminate every electrochemical reaction, but to keep corrosion within acceptable limits while avoiding scale and deposits.
Common corrosion drivers
- Low pH or low alkalinity.
- High chloride or sulfate concentration at elevated cycles.
- Under-deposit conditions that create local concentration cells.
- Microbiologically influenced corrosion.
- Galvanic effects between dissimilar metals.
- Inadequate inhibitor residual or poor chemical distribution.
- Process contamination entering the cooling circuit.
What corrosion looks like
General thinning, localized pitting, rust-colored deposits, leaking tubes and increasing iron in water can all be indicators. However, water iron alone is not a complete corrosion measurement because corrosion products can deposit elsewhere in the system.
Monitoring methods
Corrosion coupons provide a simple time-averaged measurement when installed and handled correctly. Electrical resistance or linear polarization probes can provide more frequent information. Inspection data, tube thickness and failure history are also valuable.
Control strategy
Keep pH, cycles and inhibitor concentration within the approved program limits. Prevent deposits through filtration, dispersancy and housekeeping. Maintain microbiological control because biofilm can create highly localized corrosion conditions.
Use trends
Compare corrosion results with periods of high conductivity, biocide changes, shutdowns, process leaks and chemical feed interruptions. The combination of data usually tells a clearer story than a coupon result alone.
Acceptable corrosion rates depend on metallurgy, equipment criticality and site requirements. Use plant standards or treatment-program criteria rather than a universal pass/fail number.