The surface treatment industry generates effluents with a high load of highly toxic chemicals which must be treated under increasingly stringent regulation. The aim of this study is to treat the effluents of surface treatment unit of an aeronautical industry by electrocoagulation process using aluminium electrodes. This process is used to study its performance to remove these effluents from their colloidal load, their significant amount of oxidizable material and their high levels of various metal elements (Cr, Fe, Zn, Cu and Al), under optimum conditions of pH 7, 8.6A of current intensity and 60 min of application. Electrocoagulation prosses was found to be effective in reducing turbidity (97.12%), COD (97.5%), SS (97.84%) and conductivity (96.82%), hexavalent chromium (99.99%), Zn (96.82%), Cu (94.3%), Iron (99.9%), Al (91.96 %). The treated effluent was conformed to the Moroccan standards of surface treatment discharge.