Exfoliation corrosion of aluminum alloys and their protection by coatings with metal-filled primers

Exfoliation corrosion (EC) is shown to represent a special type of stress corrosion which develops under the surface of aluminum high-alloyed alloys like 16T and B95T1. Protection against EC by using common paint coatings (PCs) is ineffective. Indoor tests demonstrate that EC can be almost completely suppressed by using PCs with zinc-filled primers (ZFPs). After 2-year tests in sea tropics, common PCs do not prevent the appearance and development of EC. At the same time, samples protected by PCs that involve ZFP EP-057 demonstrate the total absence of EC including bare surface areas up to 5 and even 10 mm wide where the coating has failed. Similar results are obtained in 6-year tests in north sea atmosphere. Potentiodynamic studies of different protection schemes confirm the electrochemical protection mechanism of aluminum alloys against EC by using ZFPs. It is shown that ZFPs can also be used during maintenance works. The advantages of metal-filled primers based on polyurethane over those based on epoxy resin are shown.Translated from Zashchita Metallov, Vol. 41, No. 1, 2005, pp. 40–51.Original Russian Text Copyright © 2005 by Sinyavskii, Kalinin, Gladyshev, Yakimova.