High Zinc in my Desal water network

[cremesti]

hey guys

i have a galvanized steel network for my desalinated sea water in which i found about 3.8 ppm of Zinc is this a sign of corrosion? is galvanized steel a bad choice of material for desal water (conductivity about 10 uS/cm)? Should I be dosing phosphate as a corrosion inhibitor?

i appreciate any advice..

regards

rami kremesti

kremesti.com

 

[bimr]

Zinc may be a corrosion product. Zinc may also be a component of a corrosion inhibitor. Zinc orthophosphate (ZOP) is a commmon corrosion inhibitor.

Galvanized steel piping would probably not be a first choice for any water distribution system. Galvanized steel piping is more common used for piping within a building.

Are you referring to a potable water system? What type of desalination system do you have? Are you presently using a corrosion inhibitor?

 

[cremesti]

hi BIMR

this system is the piping system after the storage tanks for desal water (desalinated sea water using MSF desalination). no corrosion inhibitor is currently being used.

the potable water system comes downstream. also there the LSI is -ve despite the remin filters. the pH is too low (about 7) and already a C-steel heater has corroded...

regards

rami

 

[stanier]

I suggest you should be buffering the desalinated water with lime and CO2.

The materials of choice for the water distribition would be thermopleastics such as PVC-U, PVC-M, PVC-O, ABS or PE. Some would argue that a cement lined product sould be used. The unbuffered water would leach the calcium form the lining and it would fail.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[bimr]

I assume you have a "remin filter" using calcite. Calcite filters are generally more effective for increasing the pH when operated at higher pH levels. Since your pH is low, the remin filter will not work satisfactorily.

So yes, the zinc is most likely a corrosion product.

A corrosion inhibitor is not recommended since the most economical method to reduce corrosion is to raise the pH of the water.

You will be better off with a different remineralization method.

As Stanier suggests, you can use a remineralization method that uses lime, caustic soda, or sodium carbonate.

The method and equipment that will be necessary to do this will depend somewhat on the capacity of your water system.

http://desline.com/articoli/6327.pdf

http://www.dlr.de/tt/Portaldata/41/...WP06_AQUA-CSP-Environmental-Impacts-Final.pdf

http://www.eurekascientific.co.za/brochures/Case Studeis/CO2 for Potable Water.pdf