Powder Pulse Plating

Electroplating is a common method of obtaining metallic coatings on a surface. Generally, the metal salt is introduced into solution and a direct current is applied to the material that is to be coated. In this thesis, an alternative approach is investigated, namely the metal is introduced onto the metal surface as a powder and a pulsed current is applied to firstly dissolve some of the powder and the polarity is reversed so that the metal is then deposited. This fuses the powder to itself and to the substrate. In the current study, deep eutectic solvents were used as the electrolytes and two metals were chosen; zinc and copper. Initially the dissolution and deposition of the pure metals were investigated. It was found that far from being simple dissolution and deposition processes insoluble films were formed on the electrode surface during both deposition and dissolution for zinc and during dissolution for copper. Powder pulse plating was successfully demonstrated if the current pulse characteristics were kept within a window of size and duration which avoided these insoluble films. It was found that large metallic particles could be used when the substrate was held in a horizontal orientation and small particles were best when the electrode was held vertically. For both metals it was demonstrated that super-efficient deposition could be obtained (Faradaic current efficiency in the cathodic pulse > 100%). It was also shown that composite materials could be produced by mixing inert particles with the metallic powder.