The inhibiting effects of 2-mercapto-4-amino-5-nitroso-6-hydroxy pyrimidine (MAP) at various concentrations on the copper corrosion in 3.5% NaCl solutions at 25 degrees C are examined. The inhibiting efficiency of MAP is evaluated from weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) measurements. Experimental investigations showed that MAP reduces markedly the copper corrosion in 3.5% NaCl solutions, and this reduction in corrosion rates enhances with increasing concentration of this compound. The results obtained from the different corrosion evaluation techniques are in good agreement. Polarization curves indicate that MAP is a mixed-type inhibitor. The results of EIS indicate that the value of CPEs tends to decrease and both charge transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. EFM can be used as a rapid and non-destructive technique for corrosion rate measurements without prior knowledge of Tafel constants. (C) 2010 Elsevier B.V. All rights reserved.