We are using online corrosion electrode of type electrical resistance to monitore corrsoion rate in cooling system of cappacity 27000m3 , we use NALCO company treating program since 2 months ,( we were using KURITA program) we have 3 online probe of 2 electrodes , and 3 corrosion coupon In same place of probes, the problem we found that the reading of corrosion rate are increasing and when we checked the electrode we found some rust deposite at the end of electrode although the corrosion coupons condition is good !! We continue replace the electrode and reading is good in first two day and begin to rise again !we don’t know reason for that ,, we adjust flowrate to electrode 40 litre per hour ,, we don’t now is this rate is recommended or what ! Any help ?!
Sound like your probes corrode faster than the material you're tracking. Without knowing more about this issue it's hard to say for sure, but it could be as simple as an electrical contact between the corrosion probe and another metallic part in the system. If the metals are different, you will get increased corrosion on one and cathodic protection on another. I hope this helps.
Thanks doctor, the electrode material is carbon steel same as the cooling system pipe material ,the probe placed in pvc pipe bypass from main pipeline! Any more information you need to know the reason of this issue?
Dear Mohanad
Localized deposition on the metal probe is the main limitation that ER probe not widely used in CW applications. As these deposit can give misleading results.
Now the question is how to minimize the deposit. Therefore it is necessary to plot the water linear velocity (flow rate) as a function of as measured corrosion rate experimentally then the more or less a zero slop zone of this function indicates no significant deposition. This range of flow rate represents the optimum normal operation flow rate inside the bypass line.
Best regards
to determine the flow rate in corrosion metal liquids, in my opinion this depends on the specific gravity combined with the analysis of the flow rate formula.
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