Case histories of failures of aircraft structural members from stress corrosion cracking are cited and illustrated. Consideration is given to the magnitude and orientation of stresses which are conducive to stress corrosion cracking. Residual stresses and techniques during and after fabrication which reduce them are discussed. The mechanism by which barrier and cathodic coatings can be expected to limit stress corrosion is outlined.
Tests of both continuous and discontinuous coatings, varying thicknesses of inorganic coatings and the effect of bolt loadings and other factors are surveyed. The authors say relative effectiveness of coatings tested could not be determined by comparison of their solution potentials.
An extensive series of accelerated tests into the protective characteristics of organic and inorganic coatings against stress corrosion cracking of high-strength aluminum alloys is reported. These tests with electrolytically deposited and sprayed zinc and aluminum coatings and with organic primer and finish coats both separately and in combination failed to indicate a system which would give the desired protection and at the same time have other necessary properties. The investigations are continuing. Shot peening to introduce surface compressive stress is being investigated.
