Investigation of the Electrodeposition Parameters on the Coating Process on Open Porous Media

Abstract

Porous materials such as bones, sponges or cork are used in nature due to their light weight. Metal foams with stochastically distributed pores are such a porous bionic material based on nature. Their low weight and mechanical properties make them perfect for use in aerospace, automotive and building construction industry. To improve the mechanical properties, hybrid metal foams are produced consisting of a substrate foam with a coating applied by electrodeposition. An electrochemical coating cell consists of a positively charged anode and a negatively charged cathode. The metal of the anode is oxidised to a positively charged cation and electrons. The cation moves through the electrolyte to the cathode, where it is reduced back to the metal and electrons are consumed. Due to this process the cathode is coated with the anode material. The mass transport during the electroplating process can be divided into four parts: Convection, diffusion, migration and reaction. Convection is a forced flow, e.g. by pumping. Diffusion describes the movement caused by concentration gradients and the migration is the movement by an electric field. Reaction is the ion consumption at the cathode during the electrodeposition process and is therefore called sink. During the electrodeposition process, coating thickness inhomogeneities occur due to mass transport limitations [2,4] and lead to non‐uniform mechanical properties within the coated foams. These inhomogeneties motivate an investigation of the electrodeposition process and its parameters.