Closed Loop Water Treatment - Corrosion

Closed Loop Water Treatment - Corrosion

Hello.

I have been struggling with this closed loop over the last 6 months as the chemistry is completely out of control.

It is fed with RO permeate as the coolant with a total volume of 150 m3. Average water consumption is about 1m3 per day.

The loop is used to cool the fume hood of a copper smelter's convertors.

We are treating the water with a molybdate-based corr inhibitor along with a non-oxidising glut biocide. We also have a phosphate/polymer based antiscalant in place.

Recently, the RO plant failed and a high salt passage was experienced. This led to the conductivity/TDS increase in the loop.

Temperatures in the loop range between 60-80 deg C. 

Can someone help me figure out why there is such a high amount of corrosio ?