Structural and chemical analyzer system for the analysis of deposited airborne particles and degradation compounds present on the surface of outdoor weathering steel objects

• SCA good results in the study of atmospheric particles deposited over weathering steel.
• SEM–EDS useful for particles deposition ratio evaluation.
• Several sulfates, silicates and carbonates detected.
• Manganese is attacked by SO2 and it is dissolved from the surface of steel.
• Marine airborne is not as harmful as silicates for the evolution of the material.

The weathering steel is a high strength low alloy special kind of steel theoretically resistant to the atmospheric corrosion. In the present work, several weathering steel structures exposed to the urban atmosphere were analyzed by means of structural and chemical analyzer, a spectroscopic system that combines micro-Raman and SEM/EDS microscopy measurements in the same spot, in order to detect the deposited atmospheric material and to characterize it. Several kinds of silicates and aluminosilicates containing particles were identified on the steel surface of the analyzed works. In addition, other atmospheric particles such as calcite, charcoal and chromium rich particles were detected together with several compounds coming from the reaction of the steel and the deposited particles with the acid gases of the atmosphere. These particles have negative effects in the conservation of the weathering steel changing the visual appearance of the surface and decreasing the atmospheric resistance of the material.