ALEACIONES EUTECTOIDES ZINC-ALUMINIO + 2 - 6% DE PLATA COMO ANODOS DE SACRIFICIO

Abstract

The electrochemical properties of ZnAlAg alloys were evaluated in order to use them as sacrificial anodes. In these alloys, the eutectoid proportion (Zn-22 wt % Al) was maintained; only different contents of 2, 4 and 6 wt % silver were added. These alloys exhibited excellent mechanical properties, among them, their superplastic behavior. The evaluated parameters were: current capacity, working potential evolution and dissolution morphology in a galvanostatic-controlled procedure; evolution of the cathodic and anodic polarized potentials and cathodic current density in a procedure without galvanostatic control. Although the values of several of the above mentioned parameters were satisfactory, the two procedures clearly showed  that  the  ZnAlAg anodes passivated in  artificial sea  water.  However, a  homogenization treatment applied to the initial as-cast structures originated an appropriate performance of the galvanic anodes in a NaCl 0,5 M brine, without passivation and without the exfoliation showed in the as-cast structure