Environmental Conditions for Akaganeite Formation in Marine Atmosphere Mild Steel Corrosion Products and Its Characterization

Abstract

The corrosion of mild steel in chloride-rich atmospheres is a highly topical issue. The formation of the oxyhydroxide akaganeite (β-FeOOH) in this type of atmosphere leads to a notable acceleration of the steel corrosion process. The scientific literature contains many references to outdoor marine atmospheric tests, but so far has failed to clarify two basic matters in relation to akaganeite: the environmental conditions necessary for its formation, and its morphological characterization. Research has been performed at three atmospheric corrosion stations located at Cabo Vilano wind farm (Camariñas, Spain) at different distances from the shoreline (332, 590, and 2,400 m), with chloride deposition rates of 390, 74, and 29 mg/m2/day, respectively, with the exposure of mild steel specimens for 1 year. This paper reports the environmental conditions that generally led to the formation of akaganeite: an annual average relative humidity of around 80% or higher, and simultaneously, an annual average chloride deposition rate of approximately 60 mg/m2/day or higher. Rigorous characterization of akaganeite was performed by x-ray diffraction, scanning electron microscopy/energy dispersive spectroscopy, and transmission electron microscopy/selected area electron diffraction.

Predicción de la vida útil en servicio de edificios de 50 años expuestos a ambientes marinos

“…The highest akaganeite content (52%) (see Table 1) was yielded on samples with the highest chloride content (2.05%) (see Table 2). This result agrees well with the atmospheric corrosion of steel, as a Cl -threshold of 60 mg•m -2 •day -1 and simultaneously a relative humidity of around 80% to be necessary for the formation of akaganeite (Morcillo et al, 2015). .…”

Outdoor-Indoor Atmospheric Corrosion in a Coastal Wind Farm Located in a Tropical Island

“…Monthly average spectral wave height values (1.5-2.0 m) are sufficient to produce high monthly average salinity values ( in the ranges 60-300 and 300-1500 mg m -2 d -1 Wet Candle Method). Total run of marine winds (instead to average wind speed as expected) was the parameter having greater influence on determining the atmospheric salinity of the test site [12][13][14].…”

“…The principle of this method is the same than Wet Candle described on ISO: 9225:2012 [36]. Outdoor monthly average data (12), as well as annual average data (5 sites) with respect to distance from the sea were plotted and data was statistically processed.…”

“…The principle of this method is described on ISO: 9225:2012. Average monthly data (12) and average annual data (5) were plotted respecting distance from the sea.…”

Effect of Cu, Cr and Ni alloying elements on mechanical properties and atmospheric corrosion resistance of weathering steels in marine atmospheres of different aggressivities

“…As was noted in the results section (Table ), the presence of lepidocrocite (major phase), goethite and spinel (very minor phase) was observed by XRD (RIR) in all the studied steels. This technique does not detect the presence of akageneite, which as is well known tends to form in marine atmospheres, as has frequently been seen in numerous studies carried out by other researchers . In a previous paper, the authors established the RH and Cl − ion deposition rate necessary for the appearance of a significant amount of this oxyhydroxide: a deposition rate of ≥60 mg Cl − /m 2 · d and high TOW of the metallic surface RH ≥ 80% .…”