Particularities of indoor atmospheric corrosion of steel inside electric boxes in the tropical climate of Tabasco, Mexico

Abstract

Indoor corrosion inside electric boxes is important for the reliability of electric and electronic instruments. A parallel evaluation of indoor/outdoor atmospheric corrosion of steel, pollutants and meteorological parameters was made at two sites, i.e. a rural site and a coastal site of the Tabasco State, Mexico. Two exposure conditions were evaluated: outdoors and inside electric boxes. Very low levels of sulphur compounds have been observed at the two exposure sites and two exposure conditions. As expected, corrosion of steel in an open atmosphere is higher than indoors (electric boxes). The difference between corrosion outdoors and inside electric boxes is higher at the coastal site due to the influence of chloride deposition. Significant differences have been observed in the morphology of corrosion products formed on steel. The influence of sun radiation, rain, dew and fog causes the formation of more compact corrosion products. The influence of Time of Wetness outdoors is in some extent equivalent to the influence of relative humidity inside electric boxes. Commonly, chloride deposition is very low indoors, showing low influence on corrosion. However, in particular conditions of Tabasco coastal tropical climate, its role is significant indoors. Reliability of electric and electronic instruments could be affected.

Accelerated corrosion test and field test of steel and zinc coupons at buffer areas and cross passages in a mass rapid transit tunnel

“…These observations suggest that the tunnel may be considered an ‘indoor’ environment [33], with a lower probability for the formation of a thin water layer due to lack of water precipitation or fog indoors [34]. Assuming the extreme case of maximum relative humidity of 80% and minimum temperature at 25°C, there was also unlikely to have water condensation since the corresponding dewpoint is about 21°C.…”

Depósito por aspersión de una capa protectora de SiO2–PMMA sobre acero AISI 1036 con propiedades de barrera a contaminantes atmosféricos

“…Estas muestras se sometieron a la radiación solar, a condiciones de humedad (rocío, neblina, lluvia), a temperaturas que oscilaron entre 20 -41 °C. Se aprecia la presencia de morfología globular y laminadas identificadas como lepidocrocita (γ-FeOOH), que es un oxihidróxido de hierro, poco estable y no proporciona protección al sustrato [35]. La parte posterior de la placa que estuvo expuesta al ambiente costero, pero no a la radiación solar (Figura 11b), presenta una morfología diferente a la Figura 11a, ya que no presentó presencia de corrosión a simple vista durante el periodo de exposición, ni agrietamientos en toda la superficie de la placa como el material expuesto a la radiación solar.…”