Experimental design to study corrosivity of diesel-biodiesel mixtures on microalloyed steel

Material selection is a crucial part of industrial process and the analysis of the effects of operational variables on the corrosion plays an important role. The present study was undertaken to evaluate the corrosion of a microalloyed steel in contact whit diesel-biodiesel mixtures. A design of experiments, the analysis of variance (ANOVA) and surface response methodology (SRM) were used in order to evaluate the corrosivity of the fuel mixtures in contact with steel. The effect of biodiesel concentration, addition of multifunctional additive and immersion time were the evaluated factors to research the corrosion behavior of microalloyed API X70 steel. The response used in the exploitation of the design was the corrosion rate; it was assessed through gravimetric measurements on samples. The results of the gravimetric tests showed that the immersion time has the most significant effect on corrosion resistance, following of additive and biodiesel concentration. ANOVA and SRM revealed a decrease in the corrosion rate with immersion time, effect that suggests the formation of a protective layer on the metallic surface. It can also be concluded that the use of lignin promoted the reduction of corrosive processes, especially when mixed with biodiesel; this result was corroborated by microscopy analysis.