Abstract
The effects of both test-panel orientation and exposure angle on the atmospheric corrosion rates of carbon steel probes exposed to a marine atmosphere were investigated. Test samples were exposed in a tree-shape metallic frame with either three exposure angles of 30°, 45° and 60° and orientation north-northeast (N-NE), or eight different orientation angles around a circumference. It was found that the experimental corrosion rates of carbon steel decreased for the specimens exposed with greater exposure angles, whereas the highest corrosion rates were found for those oriented to N-NE due to the influence of the prevailing winds. The obtained data obtained were fitted using the bi-logarithmic law and its variations as to take in account the amounts of pollutants and the time of wetness (TOW) for each particular case with somewhat good agreement, although these models failed when all the effects were considered simultaneously. In this work, we propose a new mathematical model including qualitative variables to account for the effects of both exposure and orientation angles while producing the highest quality fits. The goodness of the fit was used to determine the performance of the mathematical models.
Highlights
Corrosion prevention is an essential task in many areas of society, especially in engineering applications where metals or metal alloys are used [1,2]
In a previous work [13], we developed models to predict atmospheric corrosion rates for carbon steel using statistical regression, “power-law” and other approaches that resulted in forecasts adapted to the wide variety of microclimates found in the Canary Islands (Spain)
According to the data obtained in this work, the corrosion rate decreased with increasing exposure angles of the carbon steel panels, in good agreement with previous observations by other authors for carbon steel probes exposed to different atmospheres [10,12,34,35,36,37,38]
Summary
Corrosion prevention is an essential task in many areas of society, especially in engineering applications where metals or metal alloys are used [1,2]. In a previous work [13], we developed models to predict atmospheric corrosion rates for carbon steel using statistical regression, “power-law” and other approaches that resulted in forecasts adapted to the wide variety of microclimates found in the Canary Islands (Spain) None of these models considered the effects of either the exposure angle (with respect to the horizontal) or the orientation of the tested panel samples. There are two competing phenomena likely to affect the corrosion rate: fast, dry, and wet accumulation of corrosion products The latter situation often happens in urban and industrial environments where horizontal samples will be more severely corroded that vertical ones due to the accumulation of dirt on the horizontal surface, which increases the TOW and accelerates corrosion rates [27]. The data were fitted to a novel mathematical model using qualitative variables, including both the exposure angle and orientation effects
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