A study of precipitated films formed during electrochemically driven dissolution processes

• Main Author: Hammons, Joshua Aaron
• Published: University of Birmingham 2012
• Subjects: 541.37; QD Chemistry
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545385

Precipitated surface films form when metal cations are produced faster than they can move away from the dissolving interface. This build up of cations results in supersaturation conditions, which cause a solid to precipitate. The precipitated solid affects ion transport and thus the dissolution kinetics, which ultimately control the two systems studied here. X-ray diffraction, small angle X-ray scattering and fast radiography were chosen to study the metal/solution interface in-situ, using synchrotron radiation. The AC electrograining system is a widely used industrial process whereby an alternating current is applied to aluminium plates to form a pitted surface. During this process, an Al(OH)3 surface gel (smut) forms within seconds whilst electrograining continues for several minutes in its presence. Although smut formation has been investigated previously, how the smut affects metal dissolution is currently unknown and is the primary goal of this project. The second system is a nickel “artificial pit,” which is commonly used to simulate pit propagation. In this system, a salt film is precipitated by imposing a large overpotential whilst restricting transport through a 1-D pit. Interfacial phenomena that occur during salt film formation are investigated towards an understanding of how the salt film forms.