What effect do acid waters have on metal containers?

Acid waters can have a significant corrosive effect on metal containers, leading to deep pitting of the walls. This occurs because acidic conditions can accelerate the rate of corrosion in metals, which is a chemical process where the metal undergoes degradation due to reactions with the acidic components in the water. As a result, the protective oxide layer that typically guards metal surfaces can dissolve, leading to localized areas of corrosion referred to as pitting. This can weaken the structural integrity of the metal container and potentially lead to leaks and failure over time.

In contrast, minor surface scratches and no effect at all would suggest minimal damage or interaction, which is not consistent with the known behavior of metals in acidic environments. Similarly, the notion of strengthening the metal is contradictory to the effects of corrosion, as acid exposure typically does not enhance the durability or strength of materials; rather, it undermines them. Therefore, the option indicating deep pitting accurately reflects the corrosive nature of acid waters on metal containers.