Determining the corrosion rate with INTELLO

Importance of the Topic
Understanding corrosion kinetics is essential for protecting metal structures and components in industrial, marine and infrastructure applications. Tafel analysis is a widely used electrochemical technique that provides quantitative insights into corrosion rates, polarization resistance and mechanism pathways. By characterizing anodic and cathodic reaction steps, engineers and researchers can select effective coatings, inhibitors and materials to extend service life and improve safety.

Objectives and Study Overview
This Application Note demonstrates the use of Metrohm’s INTELLO software and VIONIC potentiostat to perform Tafel analysis on aluminum immersed in artificial seawater (3.5% NaCl). The study aims to determine open circuit potential, extract Tafel slopes and calculate the corrosion current and rate under controlled laboratory conditions.

Methodology and Instrumentation
A 250 mL three‐electrode corrosion cell was assembled:

• Working electrode: aluminum disc mounted on a sample holder
• Reference electrode: Ag/AgCl
• Counter electrodes: two stainless‐steel rods
• Electrolyte: artificial seawater (3.5 % NaCl)

The INTELLO default procedure for Linear Polarization – Tafel Analysis was selected. After measuring the open circuit potential (OCP), a potential sweep from – 30 mV to + 20 mV vs OCP was applied at 50 mV/s. Tafel regions on the semi‐logarithmic current–potential plot were defined using four markers (two anodic, two cathodic) to generate linear regressions.

Main Results and Discussion
• The linear polarization (j vs E) and corresponding Tafel plots (log I vs E) revealed distinct anodic and cathodic linear regions covering more than one decade in current.
• Tafel slopes (ba for anodic, bc for cathodic) were obtained by linear regression within the selected potential ranges.
• Corrosion potential (Ecorr) and corrosion current density (icorr) were determined from the intersection of extrapolated anodic and cathodic lines.
• Using the corrosion current, the corrosion rate (mm/year) was calculated via the standard formula: CR = k·icorr·M/(n·ρ·A), where M is atomic weight, n number of electrons exchanged, ρ density and A sample area.

Benefits and Practical Applications

• Rapid and reliable determination of corrosion rates and polarization resistance
• Quantitative guidance for material selection and inhibitor evaluation
• Applicability to a wide range of metals and corrosive media
• Integration within INTELLO software streamlines experiment setup and data analysis

Future Trends and Opportunities

• Expanded use of high‐frequency Electrochemical Impedance Spectroscopy (EIS) up to 10 MHz for detailed mechanistic studies
• Automation and AI‐driven analysis to identify optimal Tafel regions and improve reproducibility
• In situ monitoring of corrosion under dynamic environmental conditions
• Development of multi‐electrode arrays for spatially resolved kinetics

Conclusion
Metrohm’s INTELLO coupled with the VIONIC potentiostat offers a versatile platform for Tafel analysis, enabling precise measurement of corrosion parameters with minimal setup time. This approach supports robust decision‐making in corrosion protection and materials development.

References
No specific literature references were provided in the original Application Note.