Electrodeposition of alloys and composites with superior corrosion and electrocatalytic properties

There has been tremendous interest in the development of electrodeposition processes for synthesizing materials applicable in different fields such as corrosion protection and advanced power sources. This interest arises due to the ease of controlling the chemical composition and the functional properties of electrodeposited metals, alloys and composites. The primary goal of this dissertation is to illustrate the use of electrochemical deposition techniques in obtaining innovative alloys and composite materials with superior corrosion and electrocatalytic properties. Further enhancement of the coating processes was achieved through the development of theoretical models.; Electrodeposition of alloys has long been used to change the surface properties of corroding metals so as to improve their resistance to corrosive agents. This dissertation features the deposition of ternary Ni-Zn-P alloys by a novel electroless process for such applications. A theoretical model based on mixed potential theory helped to identify key parameters that control the alloy properties. These coatings were targeted for replacing toxic cadmium deposits used in sacrificial protection of steel substrates. Ni-Zn-P deposits inhibit corrosion and eliminate hydrogen induced cracking better than Cd coatings.; An environmentally benign passivation process based on electrodeposition of silicate coatings was developed to replace toxic hexavalent chrome passivates. The operating parameters of the deposition process were optimized based on the material and corrosion properties of the coating. A deposition mechanism was developed for the process based on adsorption and subsequent polymerization of reacting species. This mechanism helped in developing a novel electrocatalytic method for obtaining crack-free silica coatings that imparts high corrosion resistance to underlying zinc surfaces.; Electrodeposited metals and alloys are also applicable in the next generation of batteries. As an example, electroless deposition of tin on graphite has been shown to provide a composite with superior electrocatalytic properties for application as anodes in lithium ion batteries. Tin encapsulation was used as a surface modification technique that helps in mitigating the "pulverization" of tin during cycling. The coated material exhibits increased capacity and better stability than bare carbon. Further enhancement of the composite properties has been obtained by incorporating polypyrrole.