Corrosion and stress corrosion cracking behavior of alloys in solutions relevant to gold thiosulfate leaching technology

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Hydrometallurgical processes for metal extraction deal with waste solution treatment and significant research isdedicated to improving the processes in terms of environmental issues. Gold hydrometallurgical extraction is currentlybeing performed bycyanide leaching. Due to personnel safetyand environmental issues, there is significant interest for replacing the cyanide leaching agent with thiosulfate. Barrick Gold Corporation is interested in developing the new leaching agent for their cyanide gold leaching process. The assessment of corrosion behavior of materials in concentrated thiosulfate solutions is an obstacle since no previous studyhas been performed in this medium. The overall objective of this proposal is to provide data on corrosion behavior of construction materials in thiosulfate solutions relevant to gold leaching. The final practical goal will be to decide on the alloys with the best performance in terms of chemical stabilityand stress corrosion cracking. In fundamental level, this will appreciablycontribute to the corrosion science since there is no data on corrosion behavior in concentrated thiosulfate solutions. This is particularlyimportant because of 1) interactions of thiosulfate with the surface leading to generation of sulfur and consequentlypromoting stress corrosion cracking; and 2) solution chemistryand the complications resulting from buffering capacityof thiosulfate. The innovative electrochemical techniques to be used in this studywill contribute to close the corrosion science gap in this particular environment.A PhD student, a post doctoral fellow and four summer students will be trained in this research project. This studywill help understanding the corrosion phenomenon in highlyconcentrated thiosulfate solutions. It will greatlyhelp deciding the best construction materials for this medium, which will finallyaccelerate the transition from the current cyanide-based leaching plants to more environmentally-friendlythiosulfate plants.