An improvement of a mathematical model of the galvanic iron corrosion, previously presented by one of the authors, is here proposed. The iron(III)-hydroxide formation is, now, considered in addition to the redox reaction. The PDE system, assembled on the basis of the fundamental holding electro-chemistry laws, is numerically solved by a locally refined FD method. For verification purpose we have assembled an experimental galvanic cell; in the present work, we report two tests cases, with acidic and neutral electrolitical solution, where the computed electric potential compares well with the measured experimental one.