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Corrosion in DI Water Piping  

May 13, 2009

There are corrosion in the demin water pipe(pipe material=stailess steel)frequently.
I have two questions:
1-How much is the corrosion effects of the PH of the demin water on the stinless steel pipe.
2- How can I increase the PH of the demin water to 8.5-9.5.
specification of the demin water: PH=6.5 temprature=25 (°C) total Fe=0.5 ppm
I have added phosphate(Na3Pho4)but it wasnot useful.

Mehdi Mokari
buyer - Isfahan, Iran

Really pure DI will attack stainless pipe, even 316L SS.
Since you say demineralized water, I am going to guess that you really mean softened water which has a very high chloride content, which does not get along with SS-it pits and corrodes.

Solution would be to go to RO (reverse osmosis)water.It is cheaper than DI and functional for many uses.
The equipment is a bit expensive and REQUIRES a good bit of attention to function properly for a long time.

James Watts
- FL

Can't help with your question 1, but with question 2 realise that if you add anything to the DI water it is no longer DI.

Bill Reynolds    consultant metallurgist Ballarat, Victoria, Australia

Hi Mehdi,

Re your pH problem, why or why didn't you use uPVC
pipe ... no corrosion, cheap as wurst, easy to install.

Freeman Newton - White Rock, B.C. Canada

May I suggest you eliminate the corrosion problem by using polypropylene, PVC or ABS pipework.
If you add anything to the water, it is no longer demin water and is contaminated. I also agree that good quality demin water would not normally attack stainless steel unless there are exceptional circumstances. However, if there is a high chloride level, it will do so. A simple ay to check if the water is pure is to check its conductivity - if it is above 0.01 microsiemens it is contaminated

Trevor Crichton R&D practical scientist - UK