Partially sulfonated polyaniline (SPANI) prepared by electropolymerization was studied using Raman spectroscopy (RS). The sulfonated substituent is known to induce a self-doping phenomenon, which allows conduction in SPANI in a larger pH range than in PANI. RS allows, to describe and discuss the modifications related to self-doping. It is shown that the charges organization (polaron lattice or bipolaron) on the chain is modified. Self-doping has an effect upon the rings nature, which presents a more oxidized character. The main SPANI characteristics: mean conductivity and high effect of protection against corrosion are explained, thanks to Raman results.