Studying the Tribocorrosion Mechanism

The process of tribocorrosion involves electrochemical and mechanical interaction between bodies of relative motion. Sliding wear, cavitation damage, abrasion, fretting, solid particle erosion, and tribo-oxidation are the typical mechanical components involved in the tribocorrosion process.

Basic knowledge about the tribocorrosion mechanism is important for research and development of new materials used for service applications, where the simultaneous action of mechanical and electrochemical agents on engineering components is involved. Research in this field will enormously reduce the loss of materials in the automotive, food processing, biomedical, geothermal, chemical, marine, petrochemical, and mining industries, enhancing the reliability and product performance.

Bruker’s Tribocorrosion Test System

Bruker’s Tribocorrosion test system, which is built on the UMT platform, provides precision control of speed, load, and position. The UMT’s modular design provides simplicity and high flexibility on a single software and hardware platform. Normal force and friction force are measured by the system to obtain the coefficient of friction (COF) as a function of time. A three-electrode electrochemical measurement system in the tribocorrosion cell provides the material removal rates. The test system can perform tests even at higher temperatures.

Tribocorrosion experimentation was recently performed in a solution of sodium chloride using copper as a model material (Figure 1). An alumina ball was used as a counter specimen to carry out the tribocorrosion test. A Pt-counter-electrode and a standard Ag/AgCl reference electrode were used to carry out the electrochemical polarization tests (Figure 2).

Figure 1. Tribocorrosion test of copper in chloride media.

Figure 2. A polarization plot during tribocorrosion test.

During the tribocorrosion test, electrochemical measurements were carried out with and without sliding wear. The contribution of the chemical component (K_C) to copper degradation during the tribocorrosion process was obtained using the electrochemical polarization test data. The mechanical component contribution (K_M) to copper degradation was gained by directly measuring the wear scar with and without cathodic protection, following the test.

The value of the parameter ξ was derived by calculating the ratio of K_C over K_M, which defines the degradation mechanism involved in the tribocorrosion process. This value indicates the process that predominates over the other processes (Figure 3) in a specific tribocorrosion process. A value of ξ less than 0.1 indicates that the wear is the major contributing factor for the degradation of materials. On the contrary, a ξ value greater than 10 indicates that corrosion is the predominating process for the degradation of materials. In the case of values intermediate between the two these extreme values, both corrosion and wear notably contribute to the material loss, but one of them has a relatively greater effect than the other.

Figure 3. Mechanism of tribocorrosion.

The value of ξ was 0.18 in the case of tribocorrosion of copper in chloride media. The line diagram in Figure 3 illustrates that copper is degraded by the wear-corrosion mechanism, where the mechanical wear contributes a little more than the corrosion. Wear-corrosion is also the principal mechanism for the degradation of copper in chloride media under sliding wear conditions.

Conclusion

Bruker’s tribocorrosion test system has proven to be an exceptional tool to elucidate the diverse mechanisms contributing to the degradation of materials during the tribocorrosion process.

This information has been sourced, reviewed and adapted from materials provided by Bruker Nano Surfaces.

For more information on this source, please visit Bruker Nano Surfaces.