Comparison of Reacted Film Formation of Three Different Types of Perfluoropolyethers with a Heated Steel Surface

Abstract

The production of an inorganic layer by thermal reaction of perfluoropolyethers (PFPEs) with a steel surface is investigated. Three different kinds of PFPE–types Fz, D, and B–were used for the sample oil. The reaction experiments were carried out using a “Hotwire” method in air and nitrogen atmospheres to investigate the effect of oxygen. The thickness of the reacted steel layer was derived by calculation between the electrical resistance of the test wire before and after reaction. The rate constant K of film formation was obtained by applying the parabolic law of corrosion. The results show that the value of K in the air environment was the largest for type Fz, followed by type D, and smallest for type B. It is also found that the presence of oxygen increased the rate constant K both for types Fz and D but did not increase the value of K in the case of type B. It is theorized that the formation of a reactive fluorine intermediate, such as acyl fluoride, controls the activity of PFPE and that this reactivity is accelerated by the presence of oxygen.

Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997

KEY WORDS:

• Synthetic Lubricants
• Lubricant Degradation
• Lubricant Stability
• Boundary Lubrication
• Chemistry

Notes

Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997