Prof. Christine Stephan studies corrosion mechanisms on steels such as those used in power plant boilers to determine when a component suffers damage.

Prof. Christine Stephan studies corrosion mechanisms on steels such as those used in power plant boilers to determine when a component suffers damage.

Source: BAM, photo: Michael Danner

Christiane Stephan-Scherb is a mineralogist and studies corrosion zones in steels to find out exactly when a thin film is really transformed into an area of damage.

Prof. Stephan-Scherb, a part of your work is performed using a light oven – what kind of special oven is that?

The light oven can heat steel samples up to 700 degrees Celsius in just a few minutes. Inside the oven the steel reacts with a gas e.g. sulphur dioxide. The oven can cool down again at almost the same speed.

Why do you need this rapid heating and cooling?

Conventional lab ovens take a long time to heat up and correspondingly a long time to cool down. We want to freeze reactions through rapid cooling, that is to stop them, to be able to get a glimpse into the initial corrosion mechanisms. The steel samples are high-temperature materials used in power plant boilers and the reactive gases that we work with occur in the flue gases of combustion power plants. Our chief concern is corrosion in this harsh environment. The idea came from our head of department and our lab engineer Artur Göbel developed it into a practical light oven. The equipment is innovative in corrosion research.

You are a mineralogist. What research do you do exactly?

Crystallisation in the nanometre range. The special feature is that thin films do not take hours to cool down – they do it rather quickly. I am concerned with kinetics: how quickly specific compounds form. I try to create models for such systems.

What exactly do you consider a system?

In brief: steel + a reactive environment at high temperature + corrosion zone formation. Many chemical compounds are created and I am interested in all of them. I want to know, among other things, how much sulphur penetrates the steel and when the component suffers damage.

Is this a new research approach?

Successful corrosion research has been pursued here for quite some time. There are still many basic issues that I now consider from a different scientific perspective.

… namely from the perspective of thin film research.

This is where I come from. I have spent a long time on solar cells and can import a lot of analytical experience from there.

In the past, were you concerned with light-capturing layers, and do you now look into thin film layers that may cause damage?

Yes. The goal is indeed to create reaction and behaviour models. The two analytical methods that I use are X-ray diffraction, which takes place in-situ i.e. during the reaction, or X-ray absorption spectroscopy. Both will be used at the Adlershof synchrotron. X-rays enable the corrosion layer and a variety of compounds to be tested in great detail on the platelet. This is the topic I am lecturing about at the Free University during my junior professorship.