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DI or Tap Water for Iridite Tank Make-up

When making up a new tank of Iridite chromate conversion coating, should we use DI water or tap water. Our tap water is very soft and good quality. I have been told that we have asked the manufacturer of the product and gotten a different answer depending on who we talked to.

Mary Davis
Process Engineer - Lynnwood, Washington, USA
2007

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2007

Soft water should be fine, but DI water is even better.

Plating shops have used tap water in nearly all of their processes for decades, almost always without incident. On the one hand it's simple fact that you have greater control if you don't let undefined, unmonitored tap water salts into the system so some shops have adopted the routine of only using DI water throughout. On the other hand, if the contamination from good soft water has "no observed effect", that "greater control" is only theoretical and it's hard to justify spending the extra money when you know you will observe no effect :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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Hi Mary,

We use Alodine 1200s, 600, and 1000L. We have had good luck in this area making up the chemical conversion baths with tap water, (You're right - the water is relatively soft) then replenishing evaporation and drag out with DI water.

Christopher D. Arfman
- Seattle, Washington, USA
2007

I think the real answer is that you have to get your customer to give you a definitive answer on what they want. Get them to tell you once and for all whether tap water or DI water is required. Obviously if they want DI water then you will need to adjust your unit price to cover your costs!

Brian Terry
Aerospace - Yeovil, Somerset, UK
2007