METALLIC CORROSION IN CONTACT WITH SYNTHETIC GYPSUM PORE SOLUTIONS AND GYPSUM

Measurements of the rate of corrosion of different metals in contact w ith gypsum have been carried out in solutions simulating the electroly tic environment in the micropores of gypsum as well as in blocks of th is solid material. The corrosion rates for steels immersed in. a syn t hetic gypsum pore solution are one order of magnitude higher than thos e for copper brass and galvanized steels. All these values represent e xcessive corrosion rates. To inhibit the corrosion of steel in this so lution, it is necessary to add NaNO2 in concentrations higher than 10( -2) M. The level of corrosion for bare steel in plaster is lower than, in coarse and fine gypsum, probably because of the lower particle siz e of the former material and so the lower porosity. The level of humid ity to which the blocks of gypsum are exposed has a great influence on . the corrosion rate of steel embedded into them.