Standard Methods for Aerospace Stress Analysis

9Corrosion

9.1 Introduction to Corrosion

Corrosion is defined as the electrochemical deterioration of a metal due to its chemical interactions with the surrounding parts and environment. Corrosion can occur because the part is metallic, interacts with dissimilar conductive material, there is conductive fluid at the location of contact, and there is electrical contact between the metal and dissimilar conductive material. A typical surface corrosion at the holes where fasteners and rivets are secured is shown in Figure 9.1.

Galvanic corrosion can occur, which results from the contact of dissimilar metal parts in the presence of a conductor. Where the insulation between the surfaces of the metal parts in contact has been damaged or broken, galvanic corrosion occurs. Figure 9.2 illustrates galvanic corrosion due to dissimilar metal parts in contact.

Aluminum alloys and stainless steels are sometimes susceptible to electrochemical corrosion where an attack along the grain boundaries of an alloy causes no uniformity of the alloy structure. This type of corrosion may be undetectable visibly, as shown in Figures 9.3 and 9.4.

On aircraft structures, there are many regions that are prone to corrosion. These regions are summarized as (a) under de‐icer boots, (b) flooring and floor supports, (c) doors, (d) galley areas, (e) areas of vehicle exhaust gases, (f) integral fuel tanks, (g) lavatory areas, and (h) battery areas per AGARD‐AG‐278, 1985.

In addition to drainage access and careful ...