Avaliação da corrosão em chapas de aço carbono com e sem revestimento organometálico, em contato com os sistemas gasolina/etanol e diesel/biodiesel

Abstract

Studies of automotive tanks corrosion are of great importance, once they aim to obtain a high quality product which causes minimal damage to the environment. This study objective was to analyze three types of flat carbon steel samples corrosion resistance in various gasoline/ethanol and diesel/biodiesel solutions. For gasoline/ethanol mixtures, the ethanol amount in the solutions were 0(E0), 20%(E20), 50%(E50), 75%(E75) and 100% ethanol (E100), and for diesel/biodieselsolutions, the amount of biodiesel added to the mixtures were 0(B0), 25%(B25), 50%(B50), 75%(B75) and biodiesel itself (B100). Two of these tested steels, used for future fabrication of fuel tank, have organometallic coating, and they were classified as A and B samples type, representing different manufacturers. The other sample was an ASTM A-36 uncoated carbon steel, named C sample. Total and partial immersion corrosion tests were performed, during a 39 weeks period, using statist method of analyses. The evaluation was performed by measuring the percentage of samples mass variation. Samples surfaces, before and after immersions, as well as the corrosion products formed on these surfaces, were evaluated by Stereomicroscopy images and Scanning Electron Microscopy (SEM) analyses. Energy Dispersive Spectroscopy (EDS) qualitative and semi-quantitative analyses were also performed on the samples surfaces. From the tests results, it could be observed that, although the weight loss for all samples was not significant,localized corrosion (or pitting) was detected on the uncoated coupons surfaces. Coated samples (A and B) demonstrated high corrosion resistant in all tested mixtures, suggesting that the organometallic coating provided a physical barrier which protected the substrates against corrosion in the studied solutions.