Screening and performance study of corrosion inhibitors in Cu-Ag ions sterilization system of central air conditioning circulating cooling water

Purpose This study aims to explore how Cu2+ and Ag+ (Cu-Ag) ions used for sterilization affect the corrosion of Q235 carbon steel (Q235) and T2 red copper (T2) in central air conditioning circulating cooling water systems. This study also evaluates the effectiveness and mechanisms of composite inhibitors in this setting. Design/methodology/approach Using techniques including rotation specimen method and polarization curve analysis, this study examined the impact of Cu-Ag ions on metal corrosion. Based on the above methods, this paper also identified an effective composite inhibitor. And its mechanism was studied through X-ray photoelectron spectrometer analysis. Findings Cu-Ag ions do accelerate corrosion of two metals in the system. Sodium nitrite (NaNO2) above 400 mg/L inhibits corrosion for Q235 but less so for T2. The mix of NaNO2 and benzotriazole can have synergistic or antagonistic effects. An optimized composite corrosion inhibitor comprising 600 mg/L NaNO2 and 1 mg/L benzotriazole protects both metals. Under the harshest conditions of eight-times concentrated system, the corrosion rates of Q235 and T2 could diminish to 0.0083 mm/a and 0.0015 mm/a, respectively. X-ray photoelectron spectrometer shows it forms passivation layer on two metals’ surfaces. Originality/value This study reveals Cu-Ag ions’ accelerating effect on two metals’ corrosion and evaluates the composite inhibitor’s effectiveness in this setting. The results of this study provide insights and practical guidance for protecting metals in central air conditioning cooling water systems using Cu-Ag ions for sterilization. They can help address corrosion protection issues in such systems.