Corrosion Engineering MCP Server

# NRL Polarization Curve Coefficient Files - Provenance ## Source **Repository**: USNavalResearchLaboratory/corrosion-modeling-applications **URL**: https://github.com/USNavalResearchLaboratory/corrosion-modeling-applications **Directory**: `polarization-curve-modeling/` **License**: Public domain (U.S. Federal Government work) **Retrieved**: 2025-10-19 ## Author **Steven A. Policastro, Ph.D.** Center for Corrosion Science and Engineering U.S. Naval Research Laboratory 4555 Overlook Avenue SW Washington, DC 20375 Email: steven.policastro@nrl.navy.mil ## Description These CSV files contain polynomial response surface coefficients for calculating activation energies (ΔG) as functions of temperature (T) and chloride concentration (Cl⁻) for various electrochemical reactions on different alloys. ### Model Equation For each reaction type (ORR, HER, metal oxidation, passivation, pitting), the activation energy is calculated using a quadratic response surface: ``` ΔG(T, Cl⁻) = p00 + p10*Cl⁻ + p01*T + p20*Cl⁻² + p11*Cl⁻*T + p02*T² ``` Where: - `T` = Temperature (°C) - `Cl⁻` = Chloride concentration (M) - `p00, p10, p01, p20, p11, p02` = Fitted coefficients (from CSV files) The coefficients were obtained by fitting experimental polarization curve data from seawater exposure experiments. ## Materials Covered | Material | UNS Designation | CSV Files | |----------|----------------|-----------| | HY-80 Steel | K31820 | HY80ORRCoeffs.csv, HY80HERCoeffs.csv, HY80FeOxCoeffs.csv, HY80PitCoeffs.csv | | HY-100 Steel | K32045 | HY100ORRCoeffs.csv, HY100HERCoeffs.csv, HY100FeOxCoeffs.csv, HY100PitCoeffs.csv | | SS 316 Stainless | S31600 | SS316ORRCoeffs.csv, SS316HERCoeffs.csv, SS316PassCoeffs.csv, SS316PitCoeffs.csv | | Titanium | R50700 | TiORRCoeffs.csv, TiHERCoeffs.csv, TiPassCoeffs.csv | | Inconel 625 | N06625 | I625ORRCoeffs.csv, I625HERCoeffs.csv, I625PassCoeffs.csv | | CuNi 70-30 | C71500 | cuniORRCoeffs.csv, cuniHERCoeffs.csv, cuniCuOxCoeffs.csv | ## Reaction Types **ORR**: Oxygen Reduction Reaction (cathodic) ``` O₂ + 2H₂O + 4e⁻ → 4OH⁻ (alkaline) ``` **HER**: Hydrogen Evolution Reaction (cathodic) ``` 2H₂O + 2e⁻ → H₂ + 2OH⁻ (alkaline) ``` **Metal Oxidation** (anodic): - Fe_Ox: Fe → Fe²⁺ + 2e⁻ - Cu_Ox: Cu → Cu²⁺ + 2e⁻ **Passivation** (anodic): - Formation of protective oxide films (Fe₂O₃, Cr₂O₃, TiO₂, etc.) **Pitting** (anodic): - Localized breakdown of passive film ## CSV File Format Each CSV file contains a single row of 6 coefficients: ``` p00, p10, p01, p20, p11, p02 ``` **Example** (`HY80ORRCoeffs.csv`): ``` -579946.613541671,6699.5967741938,4967.62500000003,2133.19458896982,-40.3225806451621,-8.75000000000004 ``` ## Usage in Python ```python import pandas as pd import numpy as np # Load coefficients coeffs = pd.read_csv('HY80ORRCoeffs.csv', header=None).values[0] p00, p10, p01, p20, p11, p02 = coeffs # Calculate ΔG for given conditions def calculate_dG(T_celsius, Cl_molar): dG = (p00 + p10*Cl_molar + p01*T_celsius + p20*Cl_molar**2 + p11*Cl_molar*T_celsius + p02*T_celsius**2) return dG # Example: 25°C, 0.6 M Cl⁻ (seawater) dG_cathodic = calculate_dG(25.0, 0.6) ``` ## pH Dependence The polynomial coefficients give ΔG values without pH dependence. pH correction is applied using linear interpolation: ```python # For cathodic reactions (ORR, HER) dG_max = 1.1 * dG_nopH dG_min = 0.9 * dG_nopH m = (dG_min - dG_max) / (13 - 1) dG_cathodic = m * (pH - 13) + dG_min # For anodic reactions (metal oxidation, pitting) # Use similar interpolation with different bounds ``` ## References 1. **NRL Corrosion Modeling Applications Repository** https://github.com/USNavalResearchLaboratory/corrosion-modeling-applications 2. **Related Publications** (if available, cite NRL papers on this model) ## Validation The model has been validated against experimental polarization curve data for seawater exposure at various temperatures (5-80°C) and chloride concentrations (0.02-0.6 M). Typical accuracy: ±1 order of magnitude for current density predictions. ## Notes - Coefficients are valid for temperatures 5-80°C - Chloride concentration range: 0.02-0.6 M (freshwater to seawater) - pH range: 1-13 (with linear interpolation for pH effects) - The model uses Butler-Volmer kinetics with diffusion-limited corrections - Exchange current densities are calculated from ΔG using transition state theory --- **Vendored**: 2025-10-19 **For**: corrosion-engineering-mcp Phase 2 implementation **License**: Public domain (U.S. Government work) **Attribution**: Required - cite NRL GitHub repository and this provenance file