313 Lessons Learned:   - The additive function of lead naphthenate is a combination of physical absorption through  rubbing/ pressure and chemisorption. Bearing or t est run-in has been shown to be critical to the  generation of  proper tribofilms and extending the life of the lubricated contact .   - Depending on the mechanics in the contact (sliding versus rolling), the effect of temperature had a  significant effect. This appears to indicate that higher concentrations of lead would be required for  more severe applications involving pure sliding and/or  high temperatures as the lead is consumed  faster through reaction with surface layer steel oxides and sublayers.   - The formation and durability of the lead tribofilm is dependent on the environment with higher  performance coming under vacuum conditions. It  is also believed the lack of oxygen promotes this  life with reduced oxide formation on the steel and degradation of the lead naphthenate.  

Acknowledgements  

I would like to thank the team at Nye Lubr icants specifically  Melissa Larochelle, Paul Moses , Richie Raithel,  and Mason Wood for the tribology  testing and profilometry . 

References  

[1] Jason Galary. Mechanochemically Created Tribofilms and the Mechanics of Rolling Wear. Ph.D.  thesis, University of Massachusetts at Dartmouth, 2019.   [2] H Blok. Gear wear as related to viscosity of oil. JT Burwell, Jr., American Society of Metals, Ohio,  pages 199- 277, 1950.   [3] HC Mougey and JO Almen. Extreme pressure lubricants. Proc. API, Refi ning Div, pages 76- 94, 1931.   [4] FF Musgrave. The development and lubrication of the automotive hypoid gear. J. Inst. Pet, 32:3244, 1946.   [5] Jason T Galary. Synthetic gear lubricants go green. Gear Solutions, 8(84):24 31, 2010.   [6] Jason Galary. Study of wear properties of environmentally friendly lubricants for gearing applications  as a function of film thickness transition. In Environmentally Considerate Lubricants. ASTM  International, 2014.   [7] Jason T Galary. Efficacy of Lead Naphthenate for Wear Protection in Mixed Lubrication Regime.  Proceedings of the 44th Aerospace Mechanisms Symposium, 2018.   [8] Bernard J Hamrock and Duncan Dowson. Ball bearing lubrication: the elastohydrodynamics of  elliptical contacts. 1981.   [9] St. Pierre , Nicole. “Us e of 3D Optical Profilometry to Differentiate Between Additive Chemistry” STLE  Annual Meeting, 2017   [10] Didziulis, Stephen V., and Paul D. Fleischauer. "Chemistry of the extreme- pressure lubricant additive  lead naphthenate on steel surfaces." Langmuir 7.12 (1991): 2981- 2990.   [11] Carre, D. J., P. A. Bertrand, and J. R. Lince.  Lead naphthenate additive tribochemistry in  hydrocarbon oils . No. TR -2002 (8565) -2. AEROSPACE CORP EL SEGUNDO CA LAB  OPERATIONS, 2001.   [12] Peterangelo, Stephen C., et al. "Improved additives for multiply alkylated cyclopentane‐ based  lubricants." Lubrication Science 25.1 (2008): 31- 41.  [13] Marc Ingram, Clive Hamer, and Hugh Spikes. A new scuffing test using contra- rotation. Wear,  328:229 240, 2015.   [14] Mangolini , Filippo, Antonella Rossi, and Nicholas D. Spencer. "Influence of metallic and oxidized  iron/steel on the reactivity of triphenyl phosphorothionate in oil solution." Tribology international 44.6  (2011): 670- 683.