Abstract
Biodiesel is a renewable fuel consisting of alkyl esters, which show a higher corrosive behavior when compared with a diesel fuel. The corrosive processes by biodiesel affects the processing infrastructure of this biofuel and mechanical parts of automotives. Valves, engine blocks, and cylinder liners are gray cast iron components affected by biodiesel corrosion. The corrosion resistance of niobium carbide (NbC) coatings deposited using thermoreactive diffusion (TRD) on gray cast iron in continuous contact with diesel fuel and palm biodiesel was studied. Both coated and uncoated samples were subjected to immersion tests, cyclic oxidation at 473 K, and an electrochemical impedance spectroscopy (EIS) test. The coatings were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Both the rate of corrosion by immersion and the resistance to polarization via EIS showed the favorable behavior of niobium carbide coatings against the corrosion of palm biodiesel. The corrosion rate on samples coated with niobium carbide was three times lower than that of the gray casting samples. These results allow the conclusion that niobium carbide coatings could be a viable alternative to lessening the corrosive effects of palm biodiesel in the applications where gray cast iron is used in continuous contact with biofuel.
Highlights
Biodiesel is a renewable fuel that is defined as a mixture of alkyl esters with fatty acids derived mainly from vegetable oils or animal fats [1,2]
Several studies have found that biodiesel tends to be more corrosive than fossil diesel for materials that are in contact with biofuel throughout their life cycle [2,6]
The coarse grains can grow from these initial grains by increasing their size and number with the increase in time to form a continuous thin layer on the gray iron surface
Summary
Biodiesel is a renewable fuel that is defined as a mixture of alkyl esters with fatty acids derived mainly from vegetable oils or animal fats [1,2]. This fuel has become important worldwide as it is technically competitive, biodegradable, and environmentally clean when compared to fossil diesel [3,4]. Several studies have found that biodiesel tends to be more corrosive than fossil diesel for materials that are in contact with biofuel throughout their life cycle [2,6]. Unsaturated esters tend to be reactive, exhibiting characteristics of autooxidation, photo-oxidation, and high hygroscopicity that promote the corrosive processes of the biofuel [7]
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