Abstract
The corrosion behavior of aluminum, copper, and iron in inhibited ethylene glycol-ASTM corrosive water solutions was evaluated in a laboratory loop under isothermal and heat-flux conditions for 1000 h at temperatures between 378 and 413/sup 0/K, in static autoclave tests at 450/sup 0/K for 500 h, and by potentiodynamic polarization measurements at temperatures between 298 and 348/sup 0/K. The effect of time, temperature, and ethylene glycol concentration of the heat-transfer fluid on the extent of inhibitor depletion was determined from analyses of the reserve alkalinity, pH, and inhibitor content of the solutions. The performance of an electrochemical sensor as a monitor of fluid quality was also evaluated. A heat flux of 0.4 to 1.0 kW/m/sup 2/ did not have a significant effect on the corrosion behavior of the various materials at temperatures between 378 and 413/sup 0/K. The corrosion rates of aluminum, copper, and iron in the 50 volume percent inhibited ethylene glycol-corrosive water solution decreased as a function of time during the 1000-h test. At 413/sup 0/K, the corrosion rate of copper was considerably higher than that of iron or aluminum at low flow velocity. Significant degradation of the fluid quality, as indicated by the measurement of the pH, reserve alkalinity, and inhibitor concentrations, occurred after several hundred hours at temperatures of approx. 450/sup 0/K.
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