Role of Lysinibacillus sphaericus on aviation kerosene degradation and corrosion of 7B04 aluminum alloy

Microbial activity leads to degradation of kerosene, corrosion of pipeline and deterioration of stored products. This paper describes the use of the Fourier transform infrared spectroscopy (FT-IR), turbidimetry, pH measurements, electrochemical impedance spectroscopy (EIS), polarization curves and surface analysis to study the degradation of kerosene by Lysinibacillus sphaericus and its effect on the corrosion behavior of 7B04 aluminum alloy. A model strain was isolated from the contaminated kerosene and identified as L. sphaericus based on cloning of the 16 S rDNA gene and sequence analysis. FT-IR results showed that aliphatic protons in kerosene were degraded in the presence of L. sphaericus. SEM and EDS analysis showed that L. sphaericus colonized on the surface of aluminum alloy, formed biofilm and produced organic acids in physiological activities. Thus, the drop of pH resulted in the decrease of the cathodic depolarization, indicating the acceleration of corrosion. In addition, electrochemical measurements showed that the corrosion resistance of aluminum alloy was reduced, and the corrosion current density increased after immersion in the L. sphaericus system compared to the value in the sterile system, revealing the L. sphaericus promoted the corrosion of aluminum alloy.