B05 – Selective corrosion and passivation of solid solutions and intermetallic phases

PI(s): Daniela Zander (RWTH Aachen University, KKS)

SFB researchers: Jakub Nowak (RWTH Aachen University, KKS)

The aim of this project is to investigate the role of alloying elements (Al and Ca) on the electrochemical corrosion properties of magnesium under quasi-passive immersion conditions and, in particular, to characterize their influence on the potential formation of defect phases at the substrate/oxide interface.
This will develop a mechanistic understanding considering selective corrosion mechanisms as well as passivation in simple aqueous environments. For the first time, this establishes the concept of defect phase, in this case DPD Surfaces, in corrosion science.

The key scientific questions to be addressed are:

• What are the electrochemical properties/reactions of the dissolution, passivation initiation and growth of polycrystalline solid solution crystals and intermetallic phases?

• Which are the dominant effects on aqueous corrosion in dependence of the local electrochemical character of anodic (Ca) and cathodic acting (Al) alloying elements?

• How do corrosion mechanisms depend on the grain boundary and dislocation defect phases intersecting the surface?

• How can these results be transferred to an interface related mechanistic corrosion model?

Methods used are:

• Direct current (DC) / alternating current (AC) corrosion measurements

• Scanning vibrating electrode techniques / Scanning ion-selective electrode techniques (SVET/SIET)

• Inductively coupled plasma mass spectrometry (ICP-MS)

• X-ray photoelectron spectroscopy (XPS)

• in-situ TEM (with B01)

• Scanning Electron Microscopy (SEM + EDS)