Corrosion inhibitors are the chemically active molecules which on adsorption protect the thin films or substrate materials from corrosion. The corrosion protection efficiency of the molecules adsorbed, can be studied by adopting several experimental procedures. Conventionally followed and most reliable technique is weight loss method. The instrumental techniques include, Potentiodynamic polarization or Tafel plots, Electrochemical impedance spectroscopy and Chronoamperometry. The theoretical technique which stands extraordinary is Quantum mechanical methods which involves the theoretical approach to evaluate the efficiency of the molecules in required application. In this chapter, principles of all the above techniques are discussed in detail with experimental procedures.