It's obviously corroded If the water contains impurities such as salts, it is particularly easy to corrode when it comes into contact with the aluminum surface. Even if clean water comes into contact with the untreated aluminum surface, it won't be long before it corrodes and fogs the surface. We once shipped a batch of aluminum to Taiwan Province Province by sea, and the packaging film was well sealed. When we opened it in Taiwan Province Province, we found that after aging treatment, there were pieces of white corrosion blocks on the aluminum surface of the outer layer of your 7xxx alloy (mainly due to the temperature difference between land and sea, which caused air moisture to condense inside, and salt in the ocean air infiltrated into it), resulting in precipitates. Because there is a local potential difference between the substrate and the precipitate after aluminum alloy is exposed to water without surface treatment, many micro-batteries will produce electrochemical corrosion and there are many corrosion pits.