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How does DI water affect a cleaning process?

August 27, 2010

I was considering using DI water during a cleaning process. However, given that pure water, specifically DI, may act as an acid in presence of a strong base (e.g. detergent), how may it affect the cleaning? I mean, can it become acidic enough as to neutralize part of the detergent and jeopardize the cleaning results? I know that DI water becomes more acidic if in contact with CO2, but to what extent?
Thanks for your help. I really enjoy reading your answers; I learn so much from them!

Cg Gdiaz
process engineer - Guaynabo, Puerto Rico

simultaneous replies

Dear Cg Gdiaz

No, the DI will not negatively influence your cleaner, even the opposite, if you use e.g. city water with dissolved salts it will consume some of your cleaner to "neutralize" these salts. D.I water is very pure and therefore unstable in pH (You can't even reliable measure the pH of it) and will have no chance to neutralize your alkaline cleaner.

Best regards,

Harry van der Zanden
Harry van der Zanden
- Budapest, Hungary

Most people use softened water or DI water for critical cleaning of electronic parts, and DI water for rinses for spot-free rinsing, and a surface free of ionic contamination. You needn't be concerned about the pH effect of DI water. Since it has no buffering, it will not affect pH of the cleaner.

Use of soft or DI water in the cleaner also prevents scale forming on heating coils, and rinse drain lines.

You are correct that DI water exposed to air will absorb carbon dioxide which lowers the pH. However this is just a few mg/L of CO2, and a pH drop to between 5.5 and 6.

Lyle Kirman
consultant - Cleveland Heights, Ohio

September 20, 2010

Go for it - DI water will only help your processes. The purer the make-up water the better.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

September 23, 2010

Every respondent is right, only a little explanation. DI water becomes acidic because of its hunger to dissolve anything and CO2 is readily available. Once you add the alkaline cleaner the hunger is satiated and the pH considerably raised. This purer mixture is more efficient than its contaminated counterpart made with tap water.

Guillermo Marrufo
Monterrey, NL, Mexico

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