Why can ammonia corrode metals
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There are two reasons why ammonia corrodes metals: first, ammonia can form complex ions with metal ions, and second, the atmosphere contains a large amount of oxygen. To explain it more specifically, since ammonia can form relatively stable complex ions with many metal ions, this reduces the standard electrode potential between the metal ions and the metallic elements. In terms of high school chemistry, this means that the metals become more easily oxidized. Furthermore, since Earth’s atmosphere is an oxidizing atmosphere, metals become more susceptible to oxidation, which is the phenomenon of corrosion. To be more precise, it is oxygen in the atmosphere that actually corrodes metals, while ammonia facilitates the process of corrosion. For example, copper containers cannot be used to hold ammonia, as this leads to the formation of tetraamminecopper(II) ions.
But I have a question: why does adding a small amount of water to the ammonia tank help reduce corrosion and cracking?
Is the mechanism of stress corrosion in liquid ammonia also what the original poster mentioned?
I once read a post stating that CO2 in ammonia accelerates corrosion; I’ve forgotten the principle behind it, only remembering the conclusion. It was also said that ammonia usually contains H2S, which can also cause corrosion