Alexandra Gertrud HOSU - PRACK¹, Ioan PETEAN¹, George ARGHIR², Liviu Dorel BOBOS¹, Ioan IURCUT¹ & Maria TOMOAIA COTISEL^1
1Babeş-Bolyai University, Faculty of Chemistry and Chemical Engineering, 11 Arany Janos Str., RO-400084
Cluj – Napoca, Romania, e-mail: petean.ioan@gmail.com
²Technical University of Cluj - Napoca, Faculty of Materials Science and Engineering, 103 -105 Muncii Ave., RO-
400641 Cluj – Napoca, Romania.

MARBLE NANO EROSION UNDER ACID RAIN EVIDENCED BY ATOMIC FORCE MICROSCOPY

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Marble, one of the most precious construction materials, is often used for building decorations and statues. Acid rain falls caused by industrial pollution may harm marble ornaments in a very destructivemanner. By X-ray diffraction and optical mineralogical microscopy, calcium sulphate and calcium nitrateare found to be the most important reaction products. Atomic force microscopy approach was used to reveal the erosion structure of the marble samples exposed to a moderate acid rain of pH 4 for about several weeks. Two stages of nano erosion are evidenced. The first stage affects the inside structure of calcite grain,inducing a nano erosion promotion at an exposure from 0 to 6 days. The transition to the second stage issubstantially related to the propagation of nano erosion to the grain borders, which is very pronounced onday 6. At this stage the marble ornaments are seriously damaged. The second stage corresponds to themassive erosion of the surface at day 24, with irremediable damage to the marble ornaments. The surfaceroughness was found to progressively increase during the 24 days of exposure to acid rain.