Immersion corrosion tests of carbon steel in Anhydrous ethanol from different sources

Abstract

The aim of this study was to verify the corrosiveness of anhydrous ethanol from different sources against carbon steel. For this, 21-day corrosion immersion tests were conducted using low carbon steel coupons and four different commercial anhydrous ethanol (lots A, B, C and D). The tests were performed in aerated (obtained by bubbling dried synthetic air) and de-aerated (obtained by bubbling ultrapure nitrogen) conditions. For a better control of the tests, a special test vessel was developed which allowed the maintenance of the established conditions (aerated and de-aerated) without the absorption of atmospheric humidity by ethanol. The coupons were fixed in two ways: by means of screws and by fixing them through a crevice-contained holder. In the aerated condition, no signs of corrosion were observed on any of the tested coupons. In the de-aerated condition, all coupons presented discrete dark corrosion spots preferentially at the region of attachment of the specimens (site of possible crevice formation) and some scattered dark spots on the surfaces of the coupons accompanied by a color change of the tested ethanol samples. The lot C ethanol presented a deep color change at the end of the test period. The black spots were analyzed by scanning electron microscopy (SEM) associated with an elemental analysis by energy dispersive (EDX). The ethanol samples were analyzed before and after the immersion tests to determine the acidity and the pHe. At the end of immersion experiments, a trend toward higher values of the acidity and a decrease of the pHe values were observed. This study showed that ethanol samples from different sources showed different corrosiveness, although incipient, and this corrosiveness manifested itself in de-aerated condition and preferably in the crevices.


Reference
SANTOS, C. A. L.; PANOSSIAN, Z.; BRAGAGNOLO, G. M.; MOREIRA, A. R.; BARBOSA, E.A.; SANTOS, J.V.S.; PIMENTA, G.S. Immersion corrosion tests of carbon steel in anhydrous ethanol from different sources. In: RIO PIPELINE CONFERENCE AND EXPOSITION, 2009, Rio de Janeiro. Proceedings…

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