Microbiological investigations of corrosion damages in aircraft


Hagenauer A, Hilpert R, Hack T

Date: 21 October 2008


A joint project of different European aircraft manufacturers involves the investigation of the involvement of microorganisms in corrosion damage in aircraft.!
!!!In a first step, the microflora of corrosion failures was investigated. Swab samples were taken from corroded sites and were cultured on different media under different conditions. Media and incubation conditions were suitable for the growth of aerobic and anaerobic heterotrophic bacteria, sulfate reducing bacteria, Thiobacillus (T.) thiooxidans, T. ferrooxidans. fungi, and yeasts.!
!The isolated microorganisms were identified using standard methods like microscopy, physiological tests and the test systems API and BIOLOG.!
!From 46 samples, taken from corroded sites of 7 different aeroplanes, a total of 208 microorganisms were isolated (158 bacteria, 36 yeasts, 14 mycelium-forming fungi!.!!
!The isolates were examined in the laboratory with regard to their corrosive action towards an aluminium alloy, commonly used in aircraft construction (Al-7075). Material samples were incubated in liquid media, which were inoculated with pure cultures of the respective isolates, over a period of 28 days. The degree of corrosion was determined using quantimetric analysis. Significant damages were examined metallographically.!
! Results show that the corrosive effect of the isolated microorganisms was quite different. Isolates of the genera Micrococcus, Enterococcus, Staphylococcus, Aerococcus, Bacillus, Aspergillus, and Penicillium provoked strong corrosion towards Al-7075.

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