What Does
Season Cracking Mean?
Season cracking occurs in copper-based alloys subjected to a residual or applied tensile stress and exposed to a specific environment, such as moist air containing traces of ammonia.
Season cracking is also known as stress corrosion cracking or environmental cracking.
Corrosionpedia Explains Season Cracking
Season cracking occurs most often in copper alloys containing more than 15% zinc. This cracking occurs due to a reaction between ammonia and copper, forming the cuprammonium ion, a chemical complex which is water-soluble, and hence washed from the growing cracks. Such cracking can also occur in copper and any other copper alloy, such as bronze.
Season cracking is characterized by deep, brittle cracks which penetrate into affected components. If the cracks reach a critical size, the component can suddenly fracture, sometimes with disastrous results. If the concentration of ammonia is high, then the attack is much more severe, and all exposed surfaces are subject to cracking.
Season cracking results from the conjoint action of three components:
Susceptible material (copper and its alloys)
Specific chemical species (ammonia)
Tensile stress (residual)
Season cracking can be prevented through:
Stress relief
Annealing
Avoiding ammonia
Use of materials known not to crack in the specified environment