Objective

The Polarization Curves in OLI Studio: Corrosion Analyzer offer instrumental insights, with data that can be extracted to inform material selection, safe operating windows, and stream optimization. One such property is the depassivation pH. This article will guide you through determining the depassivation pH for your system using the Polarization Curves in OLI Studio: Corrosion Analyzer.

Steps for Determining the Depassivation pH

1. Add a Corrosion Rate Calculation
2. Run a pH Survey: Start by performing a pH survey for the corrosion calculation. In the General Corrosion Rate tab, identify the pH range where the general corrosion rate decreases significantly.
3. Review the Polarization Curve: Navigate to the Polarization Curve tab and open the Variables window. This allows you to review the polarization plot at each of the surveyed pH points. It is recommended to start with the pH values identified in Step 2. 
4. Identify the Depassivation pH: In each polarization plot, examine the line representing the anodic reaction of the alloy. The depassivation pH corresponds to the first pH value where "pointed edge" disappears and the corrosion potential (indicated by the red triangle) appears on the vertical portion of the anodic curve. For increased accuracy in determining the depassivation pH, you may re-run the survey with a narrower pH range.

Conclusion

Identifying the depassivation pH using the Polarization Curves in OLI Studio: Corrosion Analyzer provides critical information for anticipating material performance and corrosion risk across varying process conditions. By systematically analyzing corrosion behavior across a pH range, users can pinpoint the threshold where passive film stability is compromised, an essential factor for defining safe operating parameters and selecting appropriate alloys. This method reflects OLI’s commitment to providing scientifically rigorous tools that enable data-driven decision-making in complex, corrosive environments.