Galvanic corrosion of aircraft bonded joints as a result of adhesive microcracks

AbstractThis paper studies the root causes of a corrosion failure found in the Airbus A320 CFM56-5b intakes. This failure occurs in a dissimilar materials joint and is strongly related to the adhesive loss of integrity at very low temperatures. The ductility reduction of the adhesive at low temperatures promotes the microcracks formation within the adhesive layer of the bonded joint, which in turn sparks the corrosion process. These microcracks allow the infiltration of dust, moisture, contaminants and salt water in the interface between the adhesive and adherents, which promotes the creation of a dielectric between the joint adherents and consequently their galvanic corrosion. Results show that the thermal strains of the dissimilar joint materials at very low temperatures significantly reduces the adhesive load margin reserved for drag loads. Some remarks are drawn in order to improve the joint corrosion resistance