In Situ Tribocorrosion: Uncovering the Science Behind Coupled Surface Damage Processes

Corrosion and wear damage are persistent, unavoidable problems that challenge Naval systems and are significant contributors to maintenance costs. When corrosion and wear are coupled, material lifetime can be severely decreased by the deleterious synergistic contributions of these processes to the protective oxide films. Subjecting corrosion resistant materials to friction and wear stresses in a corrosive environment can result in driving the surface from a protected state to actively corroding. What remains missing is the fundamental understanding of the mechanisms that operate at the junction between tribology and corrosion. We proposed to determine the physical mechanisms and reaction pathways that cause tribocorrosion, and identify the fundamental science that drives the coupled surface chemistry and wear mechanics in corrosion resistant materials. Material choices that separately meet standards for wear or corrosion resistance may, when exposed to service conditions, suffer from unexplained accelerated degradation. The speed and onset of the degraded performance can be astounding. We know little about this synergy between tribology and corrosion, and existing approaches do not adequately capture the underlying science. Today, the Navy treats corrosion and tribology resistance separately. To avoid corrosion, we often turn to high performance, passive alloys and cathodic protection. However, passive alloys and cathodic protection are not necessarily sufficient to protect surfaces from wear-induced corrosion. Furthermore, galvanic mismatches and even lubrication with seawater are unavoidable. This program worked to develop laboratory-scale science to determine the fundamental mechanisms governing tribocorrosion, and create models to predict how our materials will perform in the marine environment. A schematic of the processes of interest in the coupled wear and corrosion problem is shown in Figure 1.