Microstructure and texture engineering strategies to enhance the corrosion resistance of tin based coatings

Abstract

Coating corrosion-prone material with metal/alloy and passivated oxide layers is the primary protection method in the ever-evolving corrosion protection area. To improve the corrosion resistance of the coatings, the coating matrix is often blended to form a composite with nanomaterials like nanofibers, nanosheets, and nanoparticles. Sn and its alloys have been widely used as a corrosion-resistant material for coating applications in the electronic and canning industries due to their protective and non-toxic nature. This thesis discusses various strategies employed to enhance the corrosion protection efficiency of the Sn-based electrodeposited coatings. The first part of the thesis concerns with the investigation of the micro-texture changes in the Sn and SnCu alloy coatings with the change in the electrodeposition parameters (deposition temperature, current density, and alloy composition) and its implication on corrosion resistance. Increasing the electrodeposition current density from 5 mA.cmand#8722;2 to 80 mA.cmand#8722;2 changed the predominant crystallographic orientation from (100) to (110) while changing the electrodeposition temperature from 15and#730;C to 80and#730;C changed the dominant crystallographic orientation from (100) to (001). Electrodeposition at 70and#730;C and 20 mA.cmand#8722;2 led to the highest corrosion protection efficiency in the Sn electrodeposits, which also exhibited the highest fraction of low energy (031)[01 and#773;3] twin boundaries. The second part of the thesis work discusses the morphological, microstructural, and macrotexture changes and their implications over the corrosion protection ability of Sn and Sn-based alloy coatings when graphene oxide (GO) is incorporated into the coating matrix as a secondary phase. Four systems were studied: (i) Sn electrodeposit, (ii) Sn-Cu electrodeposit, (iii) Sn-Bi electrodeposit, and (iv) Sn-Co electrodeposit. In the Sn-GO system, the corrosion rate first decreased to a certain GO volume fraction range and increased continuously. The Sn coating with high GO volume fractions exhibited an ...