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Tarnished surface upon cleaning with DI water + saponifier

Ashok Dhawan

#26652

Tarnished surface upon cleaning with DI water + saponifier | 17 December, 2003

Anyone who has experienced and resolved tarnishing of Aluminium surface upon cleaning with DI water + saponifier. The aluminium surface is protected with conversion coating (clear) which is turning black when exposed to saponifier solution.

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#26659

Tarnished surface upon cleaning with DI water + saponifier | 17 December, 2003

Your conversion coating will not do dip about preventing corrosion of the aluminum surface when soaked in saponified DI water. * DI water has high free hydrogen ion concentration and so, is VERY corrosive. DI water is so corrosive it cannot be used in iron pipes, and will certainly tear into aluminum. Try distilled water. * Saponifiers are alkaline and have a pH >9. * Conversion coatings are very nice "paints" that allow other paints to stick to aluminum. Type 1 coatings are thicker than Type 3, which are whisper thin. Alodine 120X (Amchem) and Iridite 14-2 (Allied Research Products) are good conversion coatings.

For many, this is a cosmetic defect. If you can't live with it, consider: * Colored conversion coating. * Hard anodize and a corrosion extending seal as an alternate surface treatment. Talk to your plater about recommendations.

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Tom B

#26704

Tarnished surface upon cleaning with DI water + saponifier | 22 December, 2003

Dave is absolutely right! A question is there free standing DI water left on Parts after wash and rinse, if so this can definetly exacerbate the problem. You can try to remove excess DI water by using an IONIZER air source to blow off any water. Straight air will work but you will get into ESD issues that you don't want!

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Gary

#27253

Tarnished surface upon cleaning with DI water + saponifier | 13 February, 2004

We have an automatic washer that is using DI water in the final rinse for stainless steel surgical tools. Is this practical. Will it extented the life of the tools or just remove spots?

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Mike Konrad

#27254

Tarnished surface upon cleaning with DI water + saponifier | 13 February, 2004

Ashok,

It is most likely not the DI water that is attacking the aluminum rather it is the saponifier. DI water is only in contact with the parts for a relatively short time. If your cleaning process provides for a rapid drying cycle, you should be OK.

Most saponifiers have a pH in excess of 11. You may want to change your chemical to a non-saponifier type (Zestron, Kyzen, Petroferm) or use a saponifier with a built-in corrosion inhibitor. Corrosion inhibitor prevents the soldered pads from dulling and also, in most cases, prevents or at least inhibits the corrosion of aluminum.

Phil,

The use of DI water will not necessarily extend the like of your tools (unless improper cleaning effects the life or usefulness of the tools) but it will definitely eliminate spotting.

Mike Konrad Aqueous Technologies www.aqueoustech.com konrad@aqueoustech.com 909.944.7771

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blnorman

#27255

Tarnished surface upon cleaning with DI water + saponifier | 13 February, 2004

So Deionized water has high ion concentrations, never knew that.

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