Monday, April 11, 2011

Corrosion potential and White Rust - REALLY?

Here in the PNW (and anyone else in this range of make-up water), regardless how well you passivate and follow cooling tower manufactures recommendations, your galvanized tower basin, tubes and support structure is going to still have White Rust appear and sometimes severely.

You see, good passivation is important and should be practiced, however, all you have to do is just lose your chemical treatment or lose your solids for just a moment; more especially your pH (alkalinity) - you will fall right back into the conditions outlined by the AWT/CTI organizations that list the causes for WR in no time flat.

To avoid extremely high HTI (holding time index), we need to run these chemical programs right on the edge of the WR domain. You see we have a serious corrosion problem up here where you can run the Ryznar Indices and find you have it > 12 - or run the LSI and get -2.6; you are doomed with galvanized. The good news is that more and more contractors and customers are requested and installing SS basins.

However, when you run WCTI conditions and follow proper start-up, your white rust can and will stop and it will be protected by our silica based corrosion control in a much broader range.

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