Deionized water or DI water is used for cleaning parts, either before or after chemical solution dips during the metal finish process.
It's also used extensively in circuit board manufacturing to clean residues from soldering, hot DI water at 120º-150ºF.
Because Di water has no ions in it, it wants to become electrically balance by taking opposing ions from anything. By drawing in other minerals and contaminants, your components get clean.
There are couple choices for electric deionized water heaters: