New Perspectives on Lubricant Additive Corrosion: Comparison of Methods and Metallurgy

Traditional methods for monitoring corrosion processes and mechanisms in real time can be both time consuming and challenging to interpret, especially when evaluations at multiple temperatures are required. Reported at SAE world congress 2017 by this author, a new method for measuring the change in resistance of a thin copper wire was applied to provide a way to monitor the corrosion of copper in situ. In this work, a copper alloy in thin wire form has been used to compare the corrosion rates to pure copper. New insights on the kinetics and mechanisms of corrosion in the presence of lubricant additives over a range of operating temperatures using the wire resistance test will be discussed. The corrosion processes observed here are highly dependent upon temperature. Making assessments of corrosion performance through elevated temperature differentiation testing can provide less optimal corrosion protection at the actual operating temperature condition. This work highlights how long-duration elevated temperature testing does not provide the reassurances required for in service corrosion protection.