Volume 24, Issue 2 (March 1996)
Expanded Windows for Titanium Use in the Pulp/Paper Peroxide Bleach Plant
A corrosion database for Grade 2 titanium derived from laboratory weight-loss testing has been developed in uninhibited and inhibited alkaline 0.2–0.3 wt% H2O2 solutions at 65° to 85°C. Although titanium resistance to uninhibited hot alkaline peroxide solutions is very limited, useful resistance dramatically expands in solutions containing inhibitive species commonly existing in bleach plant processes. Effective inhibitors in descending order include Ca+2 ions, silicates, and Mg+2 salts. Addition of EDTA and DTPA chelants has no detrimental effect on Ca+2 ion inhibition unless chelant is added to excess. Based on this corrosion database, expanded application guidelines for acceptable use of Grade 2 titanium in solutions containing a maximum of 0.3 wt% H2O2 are derived at 65, 70, 80, and 85°C as a function of Ca+2 ion concentrations.