Because of their thermal stability, perfluorinated polyalkylether fluids have a great potential for use as engine oils, hydraulic fluids and greases. However, a serious drawback in their use results from the fact that certain metals, e.g., certain ones present in aircraft engine components, are corroded at temperatures above 550.degree. F in an oxidative environment. For example, when the fluids are employed as lubricants for mechanical components composed of mild steels, serious corrosion has occured at temperatures of from 550.degree. to 600.degree. F. Furthermore, stainless steels, titanium and titanium alloys are attacked by the fluids at a temperature of about 600.degree. F. Moreover, when used with titanium and titanium alloys, the fluids themselves undergo negative viscosity changes to the detriment of continued lubricating capacity.
In U.S. Pat. No. 3,393,151, issued to one of us as a coinventor on July 16, 1968, lubricants are disclosed that comprise a perfluorinated aliphatic polyether and a perfluorophenyl phosphorus compound. In U.S. Pat. No. 3,499,041, issued to one of us on Mar. 3, 1970, certain perfluoroarylphosphines are disclosed as being anti-corrosion additives for perfluorinated fluids. While the phosphorus compounds described in these patents exhibit anti-corrosion properties, at low temperatures they are only poorly soluble in perfluorinated fluids. Also, certain members of the classes of phosphorus compounds possess high volatility characteristics for long term high temperature applications. Because of these limitations, perfluorinated fluids containing such anti-corrosion additives are not completely satisfactory for use in long term, wide temperature range (-100.degree. F to &gt;600.degree. F) applications.
Accordingly, it is an object of this invention to provide an improved lubricant composition containing, as a base fluid, a perfluorinated polyalkylether.
Another object of the invention is to provide a lubricant composition that has little or no corrosive effect upon ferrous and titaniium alloys.
A further object of the invention is to provide a lubricant composition which undergoes substantially no degradation when exposed to titanium.
Still another object of the invention is to provide a lubricant composition which can be used at temperatures ranging from about -100.degree. F to 700.degree. F.
Other objects and advantages of the invention will be apparent to those skilled in the art upon consideration of the accompanying disclosure.