In the present field study, we report the exposure of weathering steels in the industrial-marine-urban environment at Ennore, located near the east coast of India for 3 years. The Corrosion products viz., iron oxyhydroxides and oxides present in the rust layers were characterized using ATR-FTIR, XRD studies and quantified using TGA analysis. The specific surface area of the rust particles formed during the corrosion process were determined using N2 adsorption isotherm studies. The morphology of the corrosion products were elucidated using SEM. ATR-FTIR and XRD studies showed that the corrosion products formed on the skyward surfaces were highly more crystalline than those on the the earthward surfaces. TGA showed that the iron oxyhydroxides were major corrosion products. N2 adsorption-desorption studies confirmed the formation of compact inner rust layers with high specific surface area (SA). SEM analysis revealed that the skyward surface was smooth and compact while the earthward surface were cracked and porous. SEM images confirmed the formation of characteristic morphological structures such as sandy crystal (lepidocrocite), needle-like (goethite), cotton ball (goethite) and cigar shaped (akaganeite) structures. Further, it revealed the formation of goethite on the skyward surface as a major constituent phase in the rust layer, which was influenced by the presence of SO2 content in the environment.
Weathering steel is widely used as a construction material due to its low cost and high corrosion resistance. The high corrosion resistance of weathering steel is attributed to the formation of dense and adherent rust layer. Atmospheric corrosion studies of weathering steels in various environments such as marine, urban and industrial areas were reported.The corrosion parameters like chloride (Cl¹), sulphur dioxide (SO2), relative humidity (RH), temperature and composition of alloying elements play a crucial role in the formation of rust products during the period of exposure in different environments.The characteristic nature of the rust layer were well studied by several researchers over the last few decades.
investigated the weathering carbon steels exposed to industrial and marine environments for 17 years
and concluded that the distributions of ¡-FeOOH phase in the inner rust layer was uniform and served as a barrier layer in the rust. studied the morphology of corrosion products formed on mild steel, which was exposed for 13 years in various environments such as marine, industrial, rural and urban. It was found that the skyward facing surface had smooth and uniform structure with low aggressivity, whereas the earthward facing surface had irregular cracked structure. Thermogravimetric analysis were used to identify and quantify the composition of the rust and this can be achieved with a small amount of sample. quantitatively analysed the composition of the rust formed in various environments using thermal analysis.
assessed the specific surface area of the rust layer by N2 and H2O adsorption studies and related this to the extent of corrosion and type of steel exposed. They showed that compact rust layers with high SA or small particle size exhibit a high corrosion resistance. have studied the long term corrosion behaviour of low alloy and plain carbon structural steel exposed to different climatic conditions for 2 years and reported the nature of rust formed, which revealed that the presence of SO2 played a vital role in reducing the corrosion rate at Chennai site when compared to other sites. Ennore is situated in the northern part of Chennai city at the east coast of South India near Bay of Bengal. Thermal power plants, petrochemical plants, ports, refineries, pharmaceutical companies and residential buildings are situated in Ennore and it is a marine-industrial-urban environment.
There are no reports on the detailed field study of rust layers formed on weathering steels subjected to long term exposure in an industrial-marine-urban environment in India. In the present investigation, thermo gravimetric analysis and N2 adsorption studies were used to understand the nature of corrosion products formed on the skyward and earthward rust layers of weathering steel exposed at Ennore, Chennai, India.
Weathering Steel in Industrial-Marine-Urban Environment
Carbon Steel, Corten Steel, Stainless steel
Rust, Bare, Powder Coated, Polished, Black Heat-resisting Paint, Iron Oxide
Diameter : 320mm--1200mm
Thickness : 1.2mm--3.0mm
Inside : Anti-wear foam paper
Outside : Plywood box
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