Environmentally mandated changes in refrigerating system working fluids have created significant changes in the interactions between these fluids and system construction materials -- metals, polymers, elastomers, and process fluids. This investigation (ASHRAE research project 887) exposed five metals and a joined metal couple commonly used in refrigerating system construction to R-134a and an additive-free branched acid polyolester lubricant. Exposures were made in sealed glass tubes at three elevated temperatures, and, to further accelerate the effects that might occur in actual systems, the exposures included two higher-than-normal moisture levels and organic acid concentrations. Anion analyses by ion chromatography were conducted on lubricants at four intervals during the aging exposures to show the rate of concentration changes of the added, and resulting, acids. Gravimetric analysis of the metals was conducted at these same intervals to show the rate of metal depletion, and scanning electron microscope analyses were made to characterize the corrosion of each metal. Infrared analyses were conducted on solid materials that formed during the exposures if quantities were sufficient, and gas chromatographic analyses were conducted on the tube vapor phase to verify refrigerant stability during aging.

Units: SI