Transient phenomena in slag reactions and corrosion

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The metals industry is a major component of the Canadian economy and to develop better control of the chemical processes used in extracting and refining metal will be to the overall benefit of our economy. Even after many years of running certain processes, it is difficult to predict the behaviour of important chemical reactions and to do this in a way that is sufficiently quantitative to ensure optimum performance. Largely this is because important conditions change during the reaction. For example, in the case of refining a liquid metal using a liquid slag, the two liquids may mix in an unpredictable and uncontrolled way for an unknown time. There are several reasons why this might happen and the current work addresses two of them. This should lead to better control of steelmaking and refining processes. Another source of transient behaviour is competing reactions. In refining we may have a desirable reaction and several others that may help or hinder this reaction. These reactions compete with each other and we would want the helpful reactions to win the competition. The current work seeks to find circumstances that enhance the beneficial reactions over those that are detrimental, but to do this we must first understand the nature of the competition. This is also important in metal refining. Transient reactions are not only an issue in metals production but are also found in corrosion. Sulphuric acid is a major industrial chemical of importance to Canada. The stainless steels used to store and transport sulphuric acid corrode in a way that makes the lifetime of the container very difficult to predict. The corrosion switches itself on and off periodically and to predict the corrosion rate we need to know for what fraction of time the corrosion is switched on. Our group has made excellent progress in understanding this and over the course of this project will develop a method to precisely predict corrosion performance in these oscillating systems.