F-7 The Effect of Corrosion Inhibitors on the Fouling Characteristics of Cooling Tower Water

J. G. Knudsen

Researchers at Oregon State University conducted an investigation to determine the effect of corrosion inhibitors on the fouling characteristics of water containing about 1000mg/l of hardness. Four hundred thirty-three fouling tests were completed.

The study involved zinc chromate and phosphate as corrosion inhibitors and antifoulants such as HEDP (1-hydroxoethylidene-1, 1-diphosphonic acid), AMP (aminoethylene phosphonate), polyacrylate, and various generic copolymers. Soluble and particulate iron (ferrous sulfate and ferric oxide respectively) were added to the water in certain tests. Researchers investigated

  • Water velocity in the test section
  • Surface temperature of the electric heater
  • pH of the water

Most of the fouling resistance-time data were fitted to an exponential equation derived from the Kern-Seaton deposition-removal model. The data were then correlated according to the HTRI fouling model. The resulting correlation provided parameters that predicted the fouling resistance-time curve and the asymptotic fouling resistance for 40 different water qualities.

This report documents the correlated data for Runs 470 through 549, summarizes the results of the investigation, and gives parameters for predicting the fouling resistance-time curve and the asymptotic fouling resistance for 40 waters. Report F-1 presents the correlation for Runs 117 through 301; Report F-3 gives the correlations for Runs 302 to 469.

Threshold operating conditions are given for a number of water qualities for which insignificant fouling [0.0001 to 0.0002 hr ft² °F/Btu (0.000017 to 0.000035 m² K/W)] may be expected. Appendix C contains the results in tabular form. These tables may be used to determine threshold operating conditions (e.g., shear stress, surface temperature) for a given water quality and asymptotic fouling resistance. The tables are considered to be most useful for those waters that display good agreement between predicted and experimental asymptotic fouling resistance and between duplicate tests.