4-dimensional digital inline holography of pitting corrosion of metal alloys

Many environmentally and economically important chemical reactions take place on surfaces at the interface between solids and gases or liquids. Some of these reactions have negative consequences, e.g. corrosion of materials. This research program will be focusing on the devastating pitting corrosion of metal alloys, specifically stainless steels and aluminum alloys. These alloys are designed to be corrosion resistant and are normally protected by an oxide layer. Nevertheless under some conditions they are affected by localized pitting corrosion, which can cause problems. About 30% of chemical plant failures are directly correlated to this form of corrosion at tremendous costs. To study the initial steps of pitting corrosion, I adapted Ellipso-Microscopy for Surface Imaging (EMSI), a technique my group had developed earlier, to be able to monitor liquid phases. We can now measure thickness changes of the protective oxide layer surrounding metastable pitting events on stainless steels and other alloys. In collaboration with theoreticians, a new mathematical model of such corrosion phenomena will be further developed and analyzed. In this project, we propose to apply a new method, Digital Inline Holography (DIH), simultaneously with EMSI and contrast enhanced optical microscopy to image particles ejected from a corroding surface. DIH represents the complete volume in front of the sample into one single image, the hologram. Mathematical algorithms can reconstruct a 3-dimentional presentation of particles within the imaged volume. This will help to understand the initial processes occurring during pitting corrosion. The long-term aim of these studies will be to find surfactants, which, even in diminutive quantities are capable of suppressing the onset of pitting corrosion. Reducing corrosion could have enormous economical and environmental consequences.