Rate evaluation of marble damage by SO2-acidity in the vicinity of stacks

A laboratory modelling for the assessment of damage to marble by the SO₂-acidity in the vicinity of stacks has been devised. The modelling is based on the role of metal oxide particulates (also emitted by smoke-stacks) which catalytically convert SO₂ to SO₃ forming H₂SO₄ (in presence of water), which has an excessively high selectivity, compared with HNO₃, for corroding marble. The requisites of the modelling are: (1) determination of composition of the marble, (2) immersion of samples of marble blocks (after measurement of surface areas) in H₂SO₄ solutions of known concentrations, maintaining pH and temperature at their initial values, (3) determination of concentrations of Ca and Mg (major components of marble) in the leachate, and thereby evaluating the mass loss of the marble, in terms of mg marble cm^–2 day^–1, for each level of H₂S0₄ concentration, (4) application of derived data for evaluation of duration (in years) for the decay of 1 cm thickness of marble block by the process of surface corrosion. From the modelling, it was found that the duration for the damage of 1 cm thickness of the marble sample used here by SO₂ acidities of 1, 5, 10, 50 and 100 ppm are 83.01, 69.02, 31.24, 8.19 and 4.31 years respectively.