Industrial wastewater does not only contribute to environmental pollution and public health problems, but also leads to equipment damage via corrosion. The present study addresses the mutual relation between pollution and corrosion with emphasis on the petroleum industry. The rate of galvanic corrosion of steel coupled with copper in oil refinery wastewater was studied by the loss in weight technique. Variables studied were; MgCl, concentration, the ratio between the cathode area and the anode area of the galvanic couple, and temperature. It was found that the rate of galvanic corrosion of steel coupled with copper increases with increasing MgCl, up to a certain value and then remains almost constant with further increase in concentration. Increasing the cathode / anode area ratio increases the rate of corrosion. Temperature was found to increase the rate of corrosion with an activation energy of 8.4 K.cal/mole which denotes that galvanic corrosion of steel in MgCI, solution is diffusion controlled reaction.