In this study, polypyrrole was deposited on the aluminium in different anions (CO (3) (2-) , NO (2) (-) , CrO (4) (2-) , DBS-). The contribution of anions to formation of polypyrrole film was investigated by using cyclic voltammetry (CV) technique. The effect of polypyrrole film on the corrosion of aluminium was searched in 0.1 M HCI solution by using potentiostatic method. For this purpose, polarization curves were obtained, corrosion current density (icorr), corrosion potential (Ecorr), polarization resistance (Rp) were determined from the polarization curves. Moreover, the percent efficiency of coating was calculated. The complexes of pyrrole pentamers and different anions (CO (3) (2-) , NO (2) (-) , CrO (4) (2-) , DBS-) were studied using ab initio quantum chemical at the Hartree-Fock (HF) levels with STO-3G, 3-21G, 6-31G(d,p)  basis sets and HOMO-LUMO energy gap is calculated by B3LYP method with 3-21G* and 6-31G(d,p) basis sets. The polypyrrole film obtained in CrO (4) (2-) anion is determined to be the most effective in prevention to pitting corrosion of aluminium as experimental and theoretical.