Adsorption and inhibition efficiency of some antipyrine derivatives on the C-steel (CS) in 1M HCl were estimated using three electrochemical techniques (electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM) and potentiodynamic polarization). Results of polarization showed that these derivatives act as mixed type inhibitors. These derivatives were adsorbed on CS surface following Langmuir adsorption model. EIS results showed that, there was a decrease in double layer capacitance (Cdl) and an increase in charge transfer resistance (Rct). Three different techniques gave concordant results.