The effects of Mn concentration on the tribocorrosion resistance of Al–Mn alloys

Abstract

An increase in the complexity and severity of service conditions demands improvements in the design of new engineering materials that are resistant to the effects of tribocorrosion. Unfortunately, there is typically a tradeoff between wear and corrosion resistance, even for important passive metals such as Al alloys. In this work, it was shown that alloying Al with Mn in supersaturated solid solution simultaneously increased the wear resistance of the Al as well as the protectiveness of the passive layer, thus improving the overall tribocorrosion resistance. Specifically, the effects of Mn alloying on the tribocorrosion behavior of magnetron-sputtered Al-Mn thin films with 5.2 at.% and 20.5 at.% Mn were investigated in a 0.6 M NaCl aqueous solution. Tribocorrosion resistance was found to be strongly affected by the alloying concentration and applied potential. Higher Mn content increased the ratio of hardness to elastic modulus (H/E) and promoted the formation of denser and more compact passive film, hence improving tribocorrosion resistance of Al. In particular, alloying with 20.5 at.% Mn led to an increase of the corrosion resistance by ~ 10 times and the hardness by ~ 8 times compared to pure Al. The total material loss during tribocorrosion was found to increase with the anodic shift of the applied potential. A galvanic cell model was used to investigate the depassivationrepassivation kinetics during tribocorrosion. It was found that alloying with 5.2 at.% Mn led to more than 10-fold reduction in the current density required to re-passivate similar worn areas of pure Al. Finally, the origin of wear-corrosion synergy was discussed based on these observations.

Effect of Dissolved Oxygen Content on Tribo-Corrosion Behavior of Monel 400 Alloy in Seawater

“…The cathodic and anodic reaction can be presented as follows: When Monel 400 alloy slides against the Al2O3 pin in seawater, the alloy will suffer serious tribo-corrosion, resulting in material loss. Generally, electrochemical corrosion and mechanical wear interact in a synergistic way; that is, corrosion will promote wear, and wear, in turn, will promote corrosion [39][40][41]. However, in this paper, the corrosion of the alloy significantly inhibits its wear, that is, ΔWc < 0, resulting in significantly greater material loss and frictional coefficient after mechanical wear tests than that after tribocorrosion tests (Figures 3 and 4).…”

Determining Tribocorrosion Rate and Wear-Corrosion Synergy of Bulk and Thin Film Aluminum Alloys

“…It can be seen that for passive alloys such as Al, the mechanical disruption during tribocorrosion leads to local breakdown/removal of the passive film on the wear track and exposing a depassivated area which leads to a decrease in the corrosion potential by ~ 20 mV. Our earlier work 16 showed that the magnitude of corrosion potential reduction is strongly related to the microstructure of the metal given the testing parameters ( e.g., applied load, sliding speed, temperature) are the same. For Al with higher hardness and finer microstructure, the same applied load may lead to a smaller depassivated area, hence smaller change in corrosion potential.…”

“…However, current evolution during tribocorrosion test at imposed cathodic or anodic potentials can be monitored. An example can be found in our previous work 16 . Figure 12 shows the current evolution of Al thin film during tribocorrosion at an imposed anodic potential of 200 mV more positive than OCP.…”

Ångström-Scale, Atomically Thin 2D Materials for Corrosion Mitigation and Passivation

“…EIS can measure the solution resistance (Rs), electric double layer capacitance (Cdl), charge transfer resistance (Rct), pore During a corrosion test, when the working electrode is at a fixed cathodic potential, corrosion is suppressed, whereas, at a fixed anodic potential, a passive film forms on the metallic surface. Thus, a potentiostatic (PS) test can be performed at fixed anodic potential to understand the structure and stability of the passive film by measuring the current, I = At −k , where A is a constant based on electrolyte and potential and k is the slope in the logarithmic I vs. logarithmic t graph indicating the passive film compactness factor [9].…”

“…However, halides and other anions can penetrate the passive films and initiate localized pitting or crevice corrosion [8]. Alloying metals can promote, strong and enduring passive film formation [9]. However, alloying changes the chemical composition and metal properties, which may not be cost effective or feasible for particular applications.…”