Abstract: The corrosion inhibition by polyacrylic acid for industrial pure iron in HCl solution was studied by using stable state polarization curves and polarization resistance ( R p). The results show that polyacrylic acid resisted and participated in iron’s anodic dissolution process, but it was not effective on irons cathodic process. The adsorption of polyacrylic acid in lower concentrations at the iron / HCl solution interface followed Temkin isotherm equation and its inhibition efficiency was found to be of a geometric blocking effect. However the inhibition efficiency of polyacrylic acid in higher concentrations was attributed to the inhibition effect on the anodic dissolution reaction of iron. The possible model for adsorption of polyacrylic acid at the iron/HCl solution interface was established. The kinetic equation of polyacrylic acid resisting and participating in the anodic dissolution process was deduced. The possible inhibition mechanism was discussed.