Pure aluminum in hot DI water

A. DI water is not exactly neutral, in fact, it is slightly acidic. Therefore a chemical reaction with the metal is not unexpected.

The thin oxide coating that naturally forms on the surface of the aluminum is not enough to protect the metal from extreme environment or physical abuse.

A. It is known that DI rinsing leaves rinsed substrates in a slightly acidic state. The reason is as follows: In the exchange process, the resins take out everything including carbon dioxide, carbonic acid/CO2 and alkalinity. This is what leaves very pure water. Once this water is released to the atmosphere from the exchange process, it will start to absorb carbon dioxide or CO2. It will continue to absorb CO2 and without alkalinity to buffer it, the pH will drop until a maximum saturation level has been reached resulting in a pH level always remaining at 5.5-6.0 pH. The reason for the slightly acidic state is that the pure water does not re-absorb the alkalinity it processed out. The oxygen level at elevated temperature is reduced. You should probably reduce your time in the DI and lower the temperatures to combat oxidation. Remember that aluminum and DI are not very compatible and this is why you see the aggressive water attacking your aluminum.