METHODOLOGY FOR DETERMINING THE EFFICIENCY OF OXYGEN REDUCING AGENTS IN AQUEOUS COOLANT

Abstract

In heat exchange systems where water is isolated from air, preventing oxygen corrosion primarily involves removing dissolved oxygen. For circulating water systems, chemical reduction of oxygen is the preferred method, with reducing agent effectiveness traditionally evaluated through various physical and chemical methods in industrial and laboratory settings. The article also presents the rationale for the need to dose oxygen reducing agents in heat supply systems where damage to heat exchangers for consumers’ hot water supply is possible. We present a widely accessible technique for chemical laboratories to determine reducing agent effectiveness by measuring its concentration before and after heating water to a specified temperature in the isolated reactor with a sample material from the heat exchange system. The presence or absence of corrosion products in the water sample after heating without air contact serves as a qualitative indicator. Using an autoclave reactor at 70°C, we observed reduction efficiencies of 75% without catalyst and 98% with catalyst (Co²⁺, 0.01 mg/dm³) for Steel 3 samples. For Steel 40 samples, efficiencies were 85% and 99%, respectively. Corrosion products were detected in water after heating without catalyst but were absent when catalyst was present. While catalyst concentration was selected based on literature data, our proposed method allows determination of minimum effective concentrations for known catalysts and facilitates investigation of novel oxygen reducing agents and their catalysts at water temperatures up to 190°C and beyond. This approach builds upon a previously developed method using the same laboratory equipment, which determines safe water composition to prevent calcium carbonate formation during heating. The methodology presented here will require adaptation to evaluate the effectiveness of corrosion inhibitors based on film-forming substances.