THE BEHAVIOR OF LEAD SILICATE AS A CORROSION-INHIBITOR FOR IRON AND ZINC

Lead silicate gives rise to Pb(II) soluble species at approximately 1 mM in an acetate buffer of pH 5.6 and 50 muM in a carbonate buffer of pH 9.6. In water, lead silicate has a negligible solubility. The Pb(II) ions in the acetate buffer lead to the deposition of a porous layer of lead when iron metal is contacted by the solution. The porous layer of lead does not reduce the iron corrosion rate in the presence or absence of oxygen. A similar situation is found for zinc. In the carbonate buffer there is no evidence for the deposition of metallic lead.