In terms of DI water being a corrosive liquid, i have gotten different feedbacks from different specialist about this.
Our main lines are made from Sch 80 PVC pipes.
We have a detergent dispenser system running on metering pumps that uses copper piping that carries DI water to flush the detergent. DI water would degrade the piping and probably leach impurities into the water. Eventually, the absolute purity of a dilution water supplied for it should not be critical as far as resistivity downstream of the dilution point is concerned. Will have a low resistivity when diluted as the molecule ionises. However, pVC has the ability to leach plasticisers into the process stream over time, and will not be top choice of piping material to maintain semiconductor ultrapure water quality. DI water is extremely corrosive. With all that said… This is as long as water naturally tends to dissociate into hydrogen and hydroxyl ions, and the ions in turn tend to exchange with any polar substances in contact with the water. Ultrapure water is easily available with current technology even in an industrial environment.
Don’t confuse pH with corrosion.
Perfectly pure water going to be neutral as there is nothing disolved in it to affect the pH.
To be honest I have to add acid to lower the pH or baking soda to raise it toward the target, It fluctuates with rain. Use. And stuff. As was noted pure water becomes hungry or ion hungry so when it contacts material that has a relatively loose hold on its ions the water pulls them away from the material causing corrosion. Basically, when water flows through a buried metal pipe or a ship moves through water, Same thing happens, for alternative reason. Cu and Cu alloys, that has data regarding Distilled water.