Metallic corrosion in contact with synthetic gypsum pore solutions and gypsum

Measurements of the rate of corrosion of different metals in contact with gypsum have been carried out in solutions simulating the electrolytic environment in the micropores of gypsum as well as in blocks of this solid material. The corrosion rates for steels immersed in. a syn thetic gypsum pore solution are one order of magnitude higher than those for copper brass and galvanized steels. All these values represent excessive corrosion rates. To inhibit the corrosion of steel in this solution, 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 size of the former material and so the lower porosity. The level of humidity to which the blocks of gypsum are exposed has a great influence on. the corrosion rate of steel embedded into them.