Efficiency of didecyldimethylammonium chloride as a microbial corrosion inhibitor for 7B04 aluminum alloy in an aircraft fuel system

The potential of didecyldimethylammonium chloride (DDAC) as a broad-spectrum antibacterial and corrosion inhibitor was investigated. Minimal inhibitory concentration tests and the agar well diffusion method were employed to evaluate DDAC’s efficacy against Sediminibacterium salmoneum , Lysinibacillus sphaericus , and Acinetobacter lwoffii , three bacterial strains that were isolated and purified from a naval aircraft fuel system. DDAC was found to be effective at a concentration of 32 mg/L with its inhibitory effect increasing as the concentration increased. The polarization curve results showed that it served as a mixed type of inhibitor that could inhibit both anodic and cathodic corrosion. The corrosion inhibition rate was 86.44% at 100 mg/L. The analysis results of electrochemical impedance spectroscopy data were consistent with the inhibition trend of the polarization curve. The adsorption of DDAC on aluminum alloy surface followed Langmuir isotherm model, with its Gibbs free energy calculated to indicate that its mechanism of corrosion inhibition was governed by both physical and chemical adsorption. Scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) results showed that DDAC formed a protective film on aluminum alloy, further demonstrating its corrosion inhibition ability. Quantum chemical calculations showed that the adsorption center of DDAC was located in the nitrogen atom, thereby offering additional insight into the corrosion inhibition mechanism of DDAC.