The manufacturer of an electrical water still has said that the failure of the heating tube elements in their unit is due to the 3ppm of chloride measured in the RO/DI feed water.
I have heard of stress corrosion cracking but a 40 mm x 5mm inch gash after only 24 to 36 hours running time post installation seems extreme. The manufacturer claims that while operating, the heating bundle was fully submerged and at a max of 150°C . The heating bundle was installed upright in a 12 inch column. The tubes are about 10 mm in diameter. Unit was electro polished and passivated (citric type) before use.
Take a look at a picture of the corrosion using the following link. What do you think the mechanism was for that kind of corrosion?
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Allan MacDonald