Webinar : The effect of alloy composition on molten salt corrosion- Dealloying, but not as we know it

The next CorroZoom webinar will take place on 2 mars 2023 at 08:00 AM Time of Est (United States and Canada) and will be given by Professor Roger Newman from the University of Toronto. The lecture is titled "The Effect of Alloy Composition on Molten Salt Corrosion - Disalloying, But Not as We Know It".

If you are interested, click here  https://osu.zoom.us/webinar/register/WN_uVkt8yKkQX-k_jodqB8zPA

Description: Roger Newman, University of Toronto

This talk will be based mainly on the recent PhD research of Dr. Touraj Ghaznavi, with other comparison material as required. Molten salt corrosion is topical in several technologies, including small modular molten-salt nuclear reactors. Our research has been focused on NiFe and NiCrFe alloys, but the general principles should be applicable to other solid-solution alloy systems that show dealloying, with the formation of nano- or micro-porous dealloyed layers.

There are two kinds of dealloying threshold, or parting limit, that are familiar at ambient temperatures in aqueous electrolytes. One is in the 50-60 at.% range of less-noble (LN) metal content (example: AuAg). The other is close to 20 at.% LN content (example: CuZn). Both these compositions have a meaning within percolation theory, as discussed by Artymowicz et al. [1]. It is recognized that increasing kinetics of surface diffusion of the more-noble (MN) metal (or surface exchange of MN metal and its ions, as in the brass example) reduce the parting limit by exposing otherwise inaccessible paths rich in LN metal. With this background, we can expect a further reduction in the parting limit at the high temperatures where we get molten salt corrosion. We can also expect that with sufficient increase in temperature, lattice diffusion of alloying elements will start to affect the kinetics and/or the morphology of the dealloyed material. Both these expectations have been realized in Dr. Ghaznavi’s work using molten chloride salts, but with several surprises along the way.

[1] D.M. Artymowicz, J. Erlebacher, and R.C. Newman, Relationship between the parting limit for de-alloying and a particular geometric high-density site percolation threshold, Philosophical Magazine 89(21) (2009) 1663-1693.