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Abstract

The effect of pre-deformation on corrosion of ASTM−A106B pipeline steel exposed to 1.7 mM sodium chloride droplets covered by simulated diluted bitumen was evaluated. The microstructures of ASTM−A106B pipeline steel with and without pre-deformation were measured by electron backscatter diffraction and optical microscope. Corrosion of pipeline steel under the chloride droplet covered by simulated diluted bitumen for 5 minutes was studied with and without pre-deformation using scanning electron microscopy. Corrosion was initiated at the surface of ASTM−A106B pipeline steel after 5 minutes of exposure. The pre-deformation increased the number of pits initiated at the steel surface and partially dissolved inclusions. Scanning electron microscopy, profilometry, and X-ray photoelectron spectroscopy measurements were used to characterize the corrosion of the specimens with and without prior deformation after 24 hours of exposure to an oil-covered droplet. The corrosion products joined together and formed a small circular ring which deviated from the geometric center of the droplet. The diameters of the circular rings for the unbent and pre-bent specimens are 2.371 ± 0.125 and 2.465 ± 0.046 mm, respectively; the distances between the circular ring centers and droplet centers are 0.599 ± 0.124 mm and 0.620 ± 0.190 mm, respectively. The average corrosion penetration of the pre-deformed specimen was 1.18 ± 0.09 times higher than that of the specimen without pre-deformation.