Weathering Steel in Industrial-Marine-Urban Environment: Field Study

Abstract

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.