Effect of valency on material removal rate in electrochemical machining of aluminium

Material removal rate (MRR) of aluminium work piece has been obtained by electrochemical machining using NaCl electrolyte at different current densities and compared with the theoretical values. It has been observed that resistance of the electrolyte solution decrease sharply with increasing current densities. The over-voltage of the system initially increases and then attains a saturation value with increasing current densities. The material removal rate, determined experimentally, almost corresponds to theoretical value with Al³⁺ state. On the other hand, taking into account over-voltage, MRR comes out be 72%. It appears that removal of a fraction of aluminium occurs in Al⁺ which subsequently gets converted into Al³⁺ through a series chemical reactions. A mechanism of such chemical reactions is proposed.