This investigation is to make comparative evaluation of the corrosion inhibiting effects of quinoline, oxine and 7-nitroso 8-hydroxy quinoline (7NHQ). In case of quinoline, and oxine, since the N atom in them functions as cation, the process involved is assumed to be cathode control. On the other hand 7-NHQ was found to form a stable chelate compound with $Fe^{++}$ ion in acidic solution and shows as anode control predominantly. After plotting polarization curves, Tafel parameters were calculated in each solution involving the inhibitors, at the same time corrosion inhibiting effects were separately measured and compared from data of both corrosion current and analytical method.