AC-83-14-2 -- Corrosivity of Glycol Antifreezes in Solar Systems PDF

The National Solar Data Network (NSDN) has been continuously monitoring the performance of solar energy systems throughout the country, for the past four years. A number of antifreeze solutions from the solar collector loops were chemically analyzed to determine the nature of the antifreezes and their effect on corrosion. The solutions had various residence times in the systems, but, with the exception of three systems, these times were unknown. It was found that a wide variety of antifreeze-corrosion inhibitor systems were being used and no pattern could be detected to indicate a preference of quality. A question was raised on toxicity, where toxic inhibitors were added to nontoxic antifreezes, i.e., proplyene glycol. The results appear to refute published laboratory studies that predict significant decomposition of the glycols. It appears the corrosion is not a serious problem for inhibited ethylene or propylene glycol solutions in properly constructed copper systems.