Metals and DI Water

Hello Vermin try gold if you are feeling rich.

I'm not sure vermin. Have you looked at stuff like this. I suppose it depends what you're using the DI for. I'm not signed in , not that I can help much . Cleaning some lens or something ? Kris

No, I have a big supply of it and the capability to produce it on demand. I use it for cooling laser cavities. DI water is so electrically resistive you can flush it between electrodes carrying thousands of Volts without causing a short. Also, it mixes well with alcohol and organic dyes for dye lasers.

Actually, it's not only metals, I also have to pick the right plastics. The problem is to keep the circulating system from re-ionizing the water as much as possible.

Brass will dissolve VERY FAST in DI water and so will copper. Gold would be good though a bit on the soft side but in reality PVDF or PVC is the best materials to use with DI Water but if you must use metal then select 316 Stainless Steel it will not corrode or shed particles as badly as must other metals.

Ultrapure water (Resistivity 18MΩcm) needs to circulate in PVDF pipework, as it is about the only material that doesn't affect it. Ultrapure water is used in the microelectronics industries.

It's not so much the pipework rather than contamination at these purities. Stop the water flowing and bugs will grow.

A plant in East Kilbride, Scotland uses 17 stages of processing to get from town mains to ultrapure, and at 80m3/d the plant occupies about half the area of a football pitch. The final ultrapure loop is in 65mm pipework, from memory.

What sort of conductivities/resistivities are under consideration, and what is the end use of the DI water? The design of a DI water system for pharmaceutical use, for example, has to take into account many factors. Materials of construction is one, and 316L S/S is a good choice. The degree of internal polish after welding is another. Minimising the number and length of branches is a third. Pipe couplings and the materials of resilient parts at joints is a fourth. The method of sterilising the pipe is another, and so on. Brass does not figure in this application, as it won't last long; the purer the water, the more aggressive it becomes, and the brass will deteriorate quickly by dissolution, increasing the ions present and reducing the quality, quite apart from the risks and effects of getting dissolved metals entering into the bloodstream...

However, for drinking water, copper, brass and bronze are quite acceptable.

OK, so I'm getting here that 316L stainless is the best way to go as far as metals are concerned. This is good considering I have a number of heat-exchangers made of the stuff. If I have plastic in the circuit, use PVC. I've heard that the more clear, vinyl-type plastics can contaminate DI water. Is this true?

My filtering system is fairly large and aggressive, and I plan to feed it with reverse osmosis water to start. I will have two ten gallon reservoirs of water, one constantly full of DI water. So, neglecting the filtration system. What is the best way to decontaminate for bio-bugs without increasing the ion population? Or will the filtration take care of that?

What is this water going to be used for? PVC is a vinyl-based plastic [polyVINYLchloride]. High purity waters will tend to leach the plasticisers out of the PVC, which is why PVDF is normally used.

Bugs will grow anywhere, given half a chance. PVDF is smooth and, provided loop velocities can be kept high and there are minimum dead-leg branches, putting ultraviolet sterilisation and disinfection equipment (two different wavelengths of UV need to be used) on the loop may be all that is required.

It sounds as though some specialist process advice could be advantageous. These people can help: http://www.watercareint.com/.

The oxygen presence or absence level (in ppm) plays crucial role to react or pasivate the metallic surface under selection. Brass or its one componenet copper or Mid steel/carbon steel remains comfortable in absence of oxygen , whereas chromium based teel like stainless steel become ctive in absence of oxygen and remains passive in presence of oxygen. So that's it to see towards the compatibility of Materials of construction to hold the DI water. Another point to be borne in mind the end use demand and sensitivity towards the quantity(in ppm) of the dissolved ions like copper, iron ans so forth. You have to keep the economy of the preservation depending on the utility value of DI. PVC type plastic materials are fine at ambient to keep DI water in healthy condition. I hope the above will suffice your thinking process to have the direction !!

How type of water you obtain: ASTM Water Grade Standards: Type I (18 MΩ / 0.056 uS/cm)- Type II (1 MΩ / 1 uS/cm) – Type III (4 MΩ / 0.25 uS/cm) – Type IV (0.2 MΩ / 5 uS/cm).

The DI water is quite aggressive with metals, even with the stainless steel; therefore it must be used plastic or glass for its storage and handling.

Exposed to environment it absorbs CO2 atmospheric. This one, when dissolving, forms carbonic acid, of there the increase of acids.

The best form to transport water DI is with pipe Nalgene.

The DI I'm using is type I... Also, what is Nalgene?

It is a plastic pipe used in biological laboratories, is your better alternative to not contaminate DI water.

See Wikipedia Nalgene for reference, and GlobalSpec for specification and use.

Nalgene has been used for bottles for storage of chemicals for at least 40 years. I've bought several in sizes from 0.1 to 10 liters at camping/mountaineering outlets over the years. Ones I bought around 40 years ago are still perfectly good!

I didn't know they made it in pipe form - I wonder what adhesive they use to join it...or heat?

Dick

Its lexan polycarbonate.

We used NAlgene for our Di water. Or we used Glass.

it was for our wet chemical anlaysis lab.

milo

The best materials for use with DI water would be plastics like polypropylene or PVC. However, if your application needs metal piping or fittings, then SS316 stainless steel is best. Brass or almost any other metal, pure or alloy, will leach tiny amounts of metal into DI water.

The best way to disinfect DI water is with UV light in the 254 nm wavelength range.

I'll agree with the 316 stainless for plumbing, but I'd drain the system when it's not in use.

Have you thought about glass? Or is there too much shock loading of the system?

A DI Loop maitained in continuos operation 24/7 with UV is the best choice. Draining a DI system means that air will be introduced to the system which means bacteria is introduced as well.

There's no shock loading at all. However, when someone says "glass" that opens a whole 'nuther can of worms. What type of glass? There's thousands, and I'll bet that some of them can contaminate DI water.

Purity means that very high power circuits don't go blam!!!

As a horseback plant engineer, I found that the lowest grades of stainless steel, 303, 304, etc. worked best with DI water. None was wonderful. Plastic, such as PVC and clear tygon work OK but require change fairly soon, due to errosion. With Tygon, you can see it when it has erroded. Inspection on a very frequent basis is mandated. We ran several hundred gallons a day of DI water out of a reverse osmosis plant. The plumber was a busy man!

No. 1 choice is PVDF. Pretty much anything else will be etched by good DI water - it is very aggresive.

Alternatives are glass or SS316. These are the next most resistant to DI, but they will etch over time as well.

Good luck!

Mark

What about polyethylene or polypropylene?

www.sae.org/technical/papers/2003-01-0804 - 28k -

Hey Vermin

Above is a link to a material study of DI water. I'm betting on ABS for plumbing.

Tom, Thanks for the Link!

milo