No abstract

A new rapid test capable of producing exfoliation in susceptible aluminum alloys within a few days has been developed. This test is useful in studies of corrosion control and alloy development. Most significant is the excellent correlation of this laboratory test with exposures to natural marine environments. It is noteworthy also that the test procedure is applicable to all types of wrought aluminum alloys. Test conditions involve cyclic exposure to acidified sodium chloride solution and to high relative humidity in a cabinet held at 95 F (35 C). This test is preferable to other laboratory procedures not only because of its speed but also because it produces readily visible exfoliation, does not require extensive specimen preparation and is not restrictive as to specimen size.

An up to date review of the stress corrosion cracking performance of wrought high strength aluminum alloys is presented. Special emphasis is placed on factors of microstructure and its directionality and the effect of ancillary alloying elements, and environmental factors. Examples of typical service problems encountered with stress corrosion cracking of high strength aluminum alloys are described along with means of combating them, such as peening, coatings, or the use of special stress corrosion resistant alloys.

Propagation rates for stress-corrosion cracking (SCC) of high-strength aluminum alloys determined with mechanically precracked double-cantilever-beam (DCB) specimens provide a quantitative means of comparing the resistance to SCC of alloys and tempers. For relatively resistant materials however, the rates can be markedly influenced by test conditions and interpretation of the crack-growth data. This paper describes a relatively simple, accelerated testing method for determining SCC velocities that rank the SCC behavior of aluminum alloys in the same order as SCC propagation rates in a seacoast or industrial atmosphere. Practical difficulties associated with this test method, however, warrant further evaluation to justify this as a primary method of testing.

No abstract