Evaluation and Improvement of Methods for Detecting Intergranular Corrosion Susceptibility in Aluminum Alloys

Present methods for determining susceptibility to intergranular corrosion in aluminum-zinc alloys were considered inadequate and attempts were made to improve or refine them. NaCl-H₂O₂ and electrolytic tests and modifications were studied. Results obtained with electrolytic method showed good correlation with results of NaCl-H₂O₂ test. The latter is believed to be more sensitive under optimum conditions, but the variables inherent in the use of H₂O₂ are difficult to control. Electrochemical processes by which the various methods accelerate intergranular corrosion are discussed. Modification of the present inspection method is recommended, and a quantitative method for assessing degree of severity of intergranular penetration suggested.

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