Posted 04 December 2012 - 01:34 AM
Thanks in advance,
Posted 04 December 2012 - 10:08 PM
I was going to give someone else a chance to answer this since I was out all day. But I am back so I guess I will wade in. First, I have never treated one of these systems. I would assume that you would use soft water since that would be preferred in all closed loop systems. Most Phosphonates require a minimum of 30 ppm of Calcium as Calcium Carbonate in order to provide adequate corrosion protection. This is NOT consistent with the idea of using soft water.
However, there is one phosphonate that does not require the presence of Calcium. It is a fairly good cathodic inhibitor in its own right. This is Hydroxyphosphonic acid (HPA). I would recommend that you use that and maintain a 15 to 20 ppm residual. There will be some initial loss due to adsorption to metal surfaces.
You mention an azole....yes, of course.
Now to the polymer. What do you intend for it to do? There are different choices for Calcium Phosphate, Calcium Sulfate, Calcium Carbonate, Silica, etc. This is always a guess depending upon what you expect to precipitate. In some formulations you might have no polymer. But since I believe that you should have soft water here, controlling iron is a likely concern. A possible choice for a soft water program would be a terpolymer that would be good for iron sequestration. Possibilities are ACUMER™ 3100 from Dow or Carbosperse™ K-781, K-797, and K-798 Acrylate Terpolymers from Lubizol.
You did not mention buffering, but you may want to put in some borate and a little caustic to maintain the pH around 8.5.
Posted 07 December 2012 - 03:04 AM
Thanks again for your input, happily I was on the right track. It's nice to have confirmation.
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