Under operating conditions, it is impossible to define precisely the environment that
was a prerequisite for SCC, as it is impossible to secure a sample of the corroding medium
before identifying the failure cause. In the presented case however, it could be determined
that the examined tube fragment was in direct contact with wet and aerated sand. This
moisture resulted from steam condensing on cold tube surface. The cooling system design
did not exclude the fresh air supply to the sand-filled duct during service life. Small
amounts of ammonia and trace amounts of nitrite and nitrate ions were found in water
extract of the sand, just as in the deposits taken from the tube surface (Table 4). Aqueous
ammonia is the principal environment that causes SCC of copper alloys. The effect of
nitrite is associates with generation of ammonia during the bare surface reaction [4].
Ammonium ions are able to form complex cations CuðNH3Þþ
2 . These ions react with