Stress Corrosion of Brass: Field Tests in Different Types of Atmosphere

Abstract

Stress corrosion tests were carried out with deep drawn cup specimens of Cu63Zn37 brass, stress-relief annealed at different temperatures after the deep drawing operation. The stress levels of the variants were determined by a cutting-up method. The specimens were exposed to the atmosphere; indoors in a storehouse with or without heating facilities and outdoors in marine, urban and rural atmospheres with or without shelter from rain. The specimens were inspected regularly during a 10-year period with respect to stress corrosion cracks, and the following conclusions were reached:

Cups of α-brass of type CuZn37 with high tensile stresses run very little risk of stress corrosion cracking in dry storage with heating facilities, although the risk of cracking cannot be completely excluded for material with a very high stress level. In a storehouse without heating, where condensation may occur occasionally, the risk of cracking is greater and exists also for material with somewhat lower stress level. On outdoor exposure the risk of stress corrosion cracking is considerably less in a marine atmosphere than in a rural or urban atmosphere; the stress corrosion risk was found to be somewhat greater under shelter from rain than on open exposure.

Brass cups of the type examined can be made proof against stress corrosion cracking by stress-relief annealing. For outdoor storage the requirement would be, e.g., annealing for 2h at a temperature of at least 300°c. For indoor storage annealing at 225°c for the same time appears to be sufficient.