Suppression of corrosion-driven hydrogen generation in gas turbine closed cooling water systems through transition from ammonium hydroxide–carbohydrazide to a nitrite-based inhibitor program

Reliable operation of closed cooling-water circuits in gas-turbine combined-cycle plants depends on appropriate cycle-chemistry design, monitoring, and control. This case study documents an engineered transition in the Gas Turbine Closed Circuit Cooling Water (GT-CCCW) system of a 414 MW combined-cycle power plant to eliminate corrosion-driven hydrogen (H 2 ) formation and stabilize operation, following the detection of significant hydrogen accumulation in the closed circuit, where gas-phase hydrogen concentrations measured after extraction reached an equivalent value of 16,035 mg L -1 (1.6%). Leak investigations confirmed no hydrogen ingress from the Gas Turbine Generator (GTG) H 2 cooler, identifying corrosion of carbon-steel surfaces under low-pH, low-dissolved-oxygen conditions as the source of H 2 evolution. The system was initially treated with ammonium hydroxide and carbohydrazide, which proved ineffective at preventing corrosion-related hydrogen generation under the prevailing operating conditions. To restore chemistry control, the plant implemented a transition to a nitrite-based corrosion-inhibition program consistent with Electric Power Research Institute (EPRI) guidance for closed-cycle cooling-water systems. Continuous monitoring showed sustained suppression during the monitoring period, with H 2 decreasing to zero within 29 days and remaining undetectable thereafter. The study provides a data-driven operating window—covering chemistry selection, dosing strategy, and monitoring frequency—that restores steady-state operation, prevents gas build-up, and maintains materials compatibility. The findings offer generalizable guidance for chemistry-based corrosion-risk control and reliable operation of industrial closed-cooling systems. • Hydrogen in GT-CCCW reduced from 1.6% to non-detect within 29 days • Corrosion-driven H 2 generation confirmed under low-pH and low-DO conditions • Nitrite-based inhibitor program effectively prevented corrosion-driven H 2 formation • Sustained H 2 suppression achieved with nitrite ≥500 ppm • Chemistry control demonstrated as a plant-scale safety and reliability measure