Home /
Search 🔍
the Site

Free personalized metal finishing help!

Re-using DI water for "water immersion test"

(-----) 2006

We currently use the water immersion test after passivation. Our unit is not plumbed and therefore needs to periodically be drained and filled with fresh DI water. Knowing how important detailed procedures can be during NADCAP audits, I need to document an appropriate interval for changing the water. I am wondering what that interval would be. Prior to the water immersion test the parts and their baskets are rinsed with DI water - so we should not be introducing any foreign contaminates that way. We do not perform a lot of passivation and often test only one small group of parts at a time, so I would like to avoid the need to flush the tank after every test.

Thank you.

Brigitte ARnold
turbine/nozzle component mfgr - Des Moines, Iowa, USA

First of two simultaneous responses -- 2006

Does your spec state what the quality of the DI water should be? If so, that would be the simplest way, just have a pre-determined conductivity/resistivity #, and once the water quality goes "out of spec", it's time to dump.

DI water will lose its quality very quickly, (especially just sitting in a tank, exposed to atmosphere) even if you are rinsing with DI just prior to putting your parts in the tank. If you really want to minimize the dumping of the tank, a simple, continuous filtering through a unibed should keep your quality in good shape, and minimize dumping.

Marc Green
Marc Green
anodizer - Boise, Idaho

Second of two simultaneous responses -- 2006

Hi Brigitte,
To establish an interval you could measure the conductivity of the water (ionic compounds dissolved in water). If your water has to be 18 megohm or less, a good in-tank conductivity probe w/ readout would be an option. Hand held meters are available and normally require frequent calibration. The tank would have to be stirred well before a sample is taken, or a reading taken from the in-tank unit. With the tank being unplumbed and aside from ionic contamination, you also run the risk of building up organics, unless you have alternate methods of agitation. Hope this helps.

Mark Baker
process engineer - Malone, New York

finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact    -    Privacy Policy    -    ©1995-2022 finishing.com, Pine Beach, New Jersey, USA