3978 (RP-748) -- Effect of Ozone on Corrosion of Carbon Steel and Copper in the Presence of HEDP and TTA in Cooling Water PDF

The stability of two corrosion inhibitors, 1-hydrozyethylidene diphosphonate (HEDP) and tolyltriazole (TTA), in the presence of 0.1 ppm of dissolved ozone in water was examined with coupon exposure tests of AISI 1010 steel and CDA 122 copper in a laboratory water-recirculating system over a range of water velocity of 0.5 to 9.5 ft/s (0.15 to 2.9 m/s) at 90degF (32degC). A linear polarisation probe was used to measure the instantaneous corrosion rate of carbon steel and copper. Water analysis was performed to determine the concentration change of the inhibitors during the corrosion tests. It was found that ozone reacted with HEDP and TTA in both soft and hard water, and the corrosion-inhibition efficiency of HEDP and TTA was reduced by ozone. Pitting occurred on carbon steel in the presence of corrosion inhibitors; ozone increased pit density at the same test conditions.

KEYWORDS: year 1996, corrosion, ozone, carbon, steel, copper, cooling, water, inhibitors, measuring, pitting corrosion, testing