Electrochemical evaluation of the compatibility of fresh and aged Novec™ 71IPA with beryllium, stainless uranium, 304L stainless steel, and 2024-T3 aluminum alloy

This study was a material compatibility assessment of four metals (beryllium, stainless uranium, 304L stainless steel, and 2024-T3 aluminum) with an environmentally benign, non-aqueous, near-azeotropic mixture of hydrofluoroether (Novec™ 7100) with 4.5 wt% isopropanol designated Novec™ 71IPA. The intent is to use the Novec™ 71IPA to clean materials in sensitive, long-term assemblies. There is concern when an aged solvent is used to clean a metal surface, it may cause corrosion due to fluoride formation as the solvent ages. Two solvent conditions, one having no detectable fluoride (fresh) and the other with ≥17 ppm fluoride (aged) were evaluated. Electrochemical evaluations using impedance spectroscopy were performed to monitor the metal surfaces for signs of reaction. Microscopic and spectroscopic techniques, including X-ray photoelectron spectroscopy, were used to characterize the metal surfaces before and after electrochemical tests. Increased impedance was observed when beryllium substrates were exposed to fresh or aged Novec™ 71IPA and was attributed to formation of organic and/or inorganic films on native beryllium oxide. Other metals exhibited insignificant changes in impedance but did show some passive film formation. Results confirmed Novec™ 71IPA, containing up to 17 ppm fluoride, had no corrosive effect on the four tested metals and may be used to safely clean them.