FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 6. Corrosion, Inspection, and Protection | 1. General | 6-4. Micro-organisms
AC 43.13-1B CHG 1
9/27/01
is not present. The metabolism of these bacte
ria requires them to obtain part of their suste
nance by oxidizing inorganic compounds, such
as iron, sulfur, hydrogen, and carbon monox
ide. The resultant chemical reactions cause
corrosion.
b. Fungi are the growths of micro
organisms that feed on organic materials.
While low humidity does not kill microbes, it
slows their growth and may prevent corrosion
damage. Ideal growth conditions for most mi
cro-organisms are temperatures between
68 and 104 °F (20 and 40 °C) and relative hu
midity between 85 and 100 percent.
d. Microbial growth must be removed
completely to avoid corrosion. Microbial
growth should be removed by hand with a firm
non-metallic bristle brush and water. Removal
of microbial growth is easier if the growth is
kept wet with water. Microbial growth may
also be removed with steam at 100 psi. Pro
tective clothing must be used when using
steam for removing microbial growth.
6-5.6-10. [RESERVED.]
c. Damage resulting from microbial
growth can occur when any of three basic
mechanisms, or a combination of these, is
brought into play. First, fungi have a tendency
to hold moisture, which contributes to other
forms of corrosion. Second, because fungi are
living organisms, they need food to survive.
This food is obtained from the material on
which the fungi are growing. Third, these mi
cro-organisms secrete corrosive fluids that at
tack many materials, including some that are
not fungi nutrient.
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