Sustained Corrosion Control Proven Over 16+ Months of Real-World Operation

At a glance

An urban retail-and-office complex in Edmonton needed reliable corrosion protection for an open cooling tower and closed chilled loop with mixed metallurgy. Guardian applied Aquaguard 508 and 810 and validated performance with long-term coupons. Result: excellent steel and copper rates over 491 days.

Key metrics

PERFORMANCE VERIFIED OVER 491 DAYS

COPPER: EXCELLENT

STEEL: LOW RATES

Why long-term coupon testing matters in mixed-metal systems

Cooling towers and chilled water loops often combine carbon steel and copper. Each metal corrodes differently, and a treatment that protects one may not fully protect the other. In a system that runs all year, even a low corrosion rate adds up over the life of the equipment.

Corrosion coupons are small metal samples installed in the system. After a set exposure time, they are pulled, cleaned and weighed, and the loss is converted to a corrosion rate in mils per year (mpy). The longer the exposure, the better the result reflects real operating conditions.

This continuously occupied Edmonton retail and office complex needed reliable protection for an open cooling tower and a closed chilled loop, and wanted long-term proof that the program was working.

Challenges

A large, continuously occupied urban complex with retail and office spaces needed reliable corrosion protection for its open cooling tower and closed chilled-water loop. With mixed metallurgy and year-round operation, even low corrosion rates could accumulate into long-term asset risk.

Solutions

Guardian implemented dedicated treatment programs tailored to each system. The cooling towers were treated with Aquaguard 508 (phosphonate-based treatment blend), while the closed chilled water loop was protected using Aquaguard 810 (filming-amine based treatment blend).

Routine monitoring ensured coupon results reflected sustained, real-world system operation.

Corrosion coupons were installed in both systems and left in service for over 16 months. Results were evaluated against Association of Water Technologies (AWT) corrosion coupon guidelines, an industry-recognized benchmark.

Results

491 days of verified corrosion control: Long-term coupon exposure confirmed stable protection under continuous operating conditions.

Excellent copper protection: Copper corrosion rates remained well below 0.1 mpy in both cooling tower and closed-loop systems.

Low, stable carbon steel corrosion: Rates supported consistent, long-term asset protection across all systems.

Data

COOLING TOWER

Cooling tower coupon testing showed stable corrosion control over 491 days in the open system. Copper corrosion measured 0.0503 mpy (within AWT “excellent”), and carbon steel measured 0.3512 mpy, indicating controlled rates over the full exposure period. Visual observations noted only localized deposits/pitting rather than widespread attack, supporting the measured results.

CHILLED LOOP

Closed loop coupon testing confirmed very low corrosion rates over 491 days. Before cleaning, coupons exhibited a dark surface film consistent with the protective filming action of Aquaguard 810. After cleaning, copper corrosion measured 0.0252 mpy and carbon steel measured 0.1645 mpy, supporting stable, long-term protection across the full exposure period.