| AVS 66th International Symposium & Exhibition | |
| Fundamental Aspects of Material Degradation Focus Topic | Thursday Sessions |
| Session DM+BI+SS-ThM |
| Session: | Material Stabilities and Technology for Degradation Protection |
| Presenter: | Dominik Dworschak, Vienna University of Technology, Austria |
| Authors: | D. Dworschak, Vienna University of Technology, Austria M. Valtiner, Vienna University of Technology, Austria |
| Correspondent: | Click to Email |
Corrosion and adhesion science usually focuses on the solid side of a liquid/solid or solid/adhesive interface. However, the only some nanometer thick interface itself is the complex transition region which drives many important processes in corrosion and delamination. The electric double layer (EDL) is a key part of the interfacial region but remains mostly neglected as a potential key player in degradation processes. Here, we will demonstrate that the EDL has an important influence on the corrosion mechanism of passivating materials in the transpassive region (material dissolution at potentials where the passive film breaks down).
We utilize an electrochemical flow cell combined with an inductively coupled mass spectrometer (ICP-MS) to enable the in-situ study of the time-resolved release of elements into solution. This provides detailed insights into the nature of the passive and transpassive condition. As model systems, we use nickel based alloys. These are essential to modern industry and uniquely tailored for a wide range of applications, which rely on high corrosion and heat resistance. In particular, we polarized a series of Ni75Cr16Fe9, Ni86Cr5Fe9 as well as Ni74Cr16Fe9Mo1 model alloys in order to understand the effect of chromium concentration and molybdenum on transpassive dissolution
In the transpassive regime we can detect the presence of protective species of chromium and molybdenum on the surface. Unexpectedly, we can demonstrate significant corrosion resistance above a critical potential where the passive film breaks down. This is traditionally known as trans passive region with bulk dissolution of metal alloys. However, we find that the EDL forms a transient passivating solution side protective layer in the transpassive region – i.e. we characterize an electric double layer induced corrosion resistance, which solely – and surprisingly - lies in the structure of the solution side. This finding has general important implications for designing degradation resistance in highly corrosive environments.