Standard Practice for Use of Mattsson's Solution of pH 7.2 to Evaluate the Stress-Corrosion Cracking Susceptibility of Copper-Zinc Alloys

Importancia y uso:

4.1 This test environment is believed to give an accelerated ranking of the relative or absolute degree of stress-corrosion cracking susceptibility for different brasses. It has been found to correlate well with the corresponding service ranking in environments that cause stress-corrosion cracking which is thought to be due to the combined presence of traces of moisture and ammonia vapor. The extent to which the accelerated ranking correlates with the ranking obtained after long-term exposure to environments containing corrodents other than ammonia is not at present known. Examples of such environments may be severe marine atmospheres (Cl⁻), severe industrial atmospheres (predominantly SO₂), and super-heated ammonia-free steam.

4.2 It is not possible at present to specify any particular time to failure (defined on the basis of any particular failure criteria) in pH 7.2 Mattsson’s solution that corresponds to a distinction between acceptable and unacceptable stress-corrosion behavior in brass alloys. Such particular correlations must be determined individually.

4.3 Mattsson's solution of pH 7.2 may also cause stress independent general and intergranular corrosion of brasses to some extent. This leads to the possibility of confusing stress-corrosion failures with mechanical failures induced by corrosion-reduced net cross sections. This danger is particularly great with small cross section specimens, high applied stress levels, long exposure periods and stress-corrosion resistant alloys. Careful metallographic examination is recommended for correct diagnosis of the cause of failure. Alternatively, unstressed control specimens may be exposed to evaluate the extent to which stress independent corrosion degrades mechanical properties.

Subcomité:

G01.06

Referida por:

G0168-17, G0030-22, G0186-05R21, G0058-85R23, G0049-85R23E01

Volúmen:

03.02

Número ICS:

77.060 (Corrosion of metals), 77.120.30 (Copper and copper alloys)

Palabras clave:

accelerated stress-corrosion cracking test environment; continuous immersion; copper-ammonium sulfate solution; copper-zinc alloys;