The purpose of this paper is to evaluate the electrochemical behaviour of corrosion inhibition of the copper-carbon steel galvanic couple (Cu-CS), exposed to reverse osmosis water (RO) used for rinsing of heat exchangers for heavy duty machinery, during manufacture. Molybdate and nitrite salts were utilized to evaluate the inhibition behaviour under galvanic couple conditions. Cu-CS couple was used as working electrodes to measure open circuit potential (OCP), potentiodynamic polarization (PP), and electrochemical impedance spectroscopy (EIS). The surface conditions were characterized by scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDS). The most effective concentration ratio between molybdate and nitrite corrosion inhibitors was determined. The morphological study indicated molybdate deposition on the anodic sites of the galvanic couple. The design of molybdate-based corrosion inhibitor developed in the present work should be applied to control galvanic corrosion of the Cu-CS couple during cleaning in the manufacture of heat exchangers.