Influence of painted steel structure orientation on its resistance to atmospheric corrosion

B.M. ROSALES

Proceedings 3rd IAS Conferenceon Uses of Steel

Instituto Argentino de Siderurgia

Lugar: San Nicolás; Año: 2006 p. 31 - 36

The heterogeneous susceptibility to Atmospheric Corrosion of painted steel structures and the way the orientation of their components define the effect of the environmental factors are analyzed The ambient characteristics (solid, liquid and gaseous contaminants) and climatic parameters of the atmosphere where the structure was exposed promote the paint weathering and corrosion of the underlying metal. But the heterogeneous symmetry of said characteristics, respect to cardinal points, to latitude, distance and orientation respect to natural and anthropogenic contamination sources, are also reflected on the different magnitude and failure type according to the orientation. Each effect will be discussed and the way in which they synergize to each other, diminishing the protective action of the organic coatings with time. The paint schemes are designed to compensate the most aggressive factors predominating in most diverse ambient, to maximize the useful life of the structure. The following meteorological parameters will be analyzed: Sun radiation, ambient temperature, relative humidity, wind, rain and any other form of water precipitation (snow, dew) determining the time of wetness (TOW) of surfaces. The effect of diverse contaminants type (ambient dust particles deposition: Al, Fe, Ca, Na and K silicates), marine salts and contaminants emitted by chimneys (metallic, carbon, organic compounds, etc., particles), liquids (mist produced by water sources) or gaseous (volcano emissions, chimneys, vehicular transit, etc.) on steel, through the paint film. Due to the fact that none paint is completely impervious the orientation and the angle respect to the horizon effects are also appreciated, even when in a lower magnitude than on unprotected steel. Factors appearing were analyzed during a study about the effect of the exposition angle of steel in the marine-industrial atmosphere of Valparaíso, Chile, superposed to heterogeneous mentioned deterioration of paint coatings.