NorsokM506CorrosionRate

Package: neqsim.process.corrosion

Standard: NORSOK M-506 (2005/2017) — “CO2 corrosion rate calculation model”

CO2 corrosion rate prediction for carbon steel pipelines and process piping in CO2-containing environments with free water. Based on the de Waard-Milliams-Lotz equations with NORSOK-specific corrections.

Calculation Steps

The calculate() method runs the following in sequence:

  1. CO2 fugacity — simplified Peng-Robinson correction on CO2 partial pressure
  2. Equilibrium pH — in-situ pH of CO2-saturated water considering temperature, fugacity, bicarbonate, and ionic strength
  3. Baseline corrosion rate — de Waard-Milliams equation (different regimes for T below/above 20 °C)
  4. pH correction factor ($F_{pH,T}$) — asymmetric formula per NORSOK M-506
  5. Scaling temperature ($T_{scale}$) — protective FeCO3 film formation threshold
  6. Scale correction factor ($F_{scale}$) — reduction when T > $T_{scale}$
  7. Wall shear stress & flow correction — from Reynolds number and Moody friction
  8. Glycol/MEG correction — reduced water activity
  9. Inhibitor efficiency — applied as $(1 - \eta)$ multiplier
  10. Final corrected rate — product of all factors
\[CR_{corrected} = CR_{baseline} \times F_{pH,T} \times F_{scale} \times F_{flow} \times F_{glycol} \times (1 - \eta_{inhibitor})\]

Applicable Range

Per NORSOK M-506:

Parameter Valid Range
Temperature 5 – 150 °C
CO2 partial pressure up to 10 bar
pH 3.5 – 6.5
Total pressure up to 1000 bar
Material Carbon steel only

Use checkApplicableRange() to verify inputs are within range.

Constructors

// Default parameters
NorsokM506CorrosionRate model = new NorsokM506CorrosionRate();

// With initial conditions
NorsokM506CorrosionRate model = new NorsokM506CorrosionRate(60.0, 100.0, 0.02);
//   temperatureC, totalPressureBara, co2MoleFraction

Input Setters

Method Default Description
setTemperatureCelsius(double) 60.0 Operating temperature (°C)
setTotalPressureBara(double) 100.0 Total system pressure (bara)
setCO2MoleFraction(double) 0.02 CO2 mole fraction in gas (0–1)
setH2SMoleFraction(double) 0.0 H2S mole fraction for sour check
setActualPH(double) -1 Measured pH (-1 = calculate from equilibrium)
setBicarbonateConcentrationMgL(double) 0.0 HCO3- for pH adjustment (mg/L)
setIonicStrengthMolL(double) 0.0 Ionic strength for activity coefficient
setFlowVelocityMs(double) 2.0 Flow velocity (m/s)
setPipeDiameterM(double) 0.254 Pipe internal diameter (m)
setLiquidDensityKgM3(double) 1000.0 Liquid density (kg/m3)
setLiquidViscosityPas(double) 0.001 Liquid viscosity (Pa.s)
setInhibitorEfficiency(double) 0.0 Inhibitor efficiency (0–1)
setGlycolWeightFraction(double) 0.0 MEG/DEG weight fraction (0–1)
setUsePHCorrection(boolean) true Enable pH correction factor
setUseScaleCorrection(boolean) true Enable scale correction factor
setUseFlowCorrection(boolean) true Enable flow correction factor

Output Getters

Call calculate() before accessing results.

Corrosion Rate Results

Method Unit Description
getCorrectedCorrosionRate() mm/yr Final corrected corrosion rate
getBaselineCorrosionRate() mm/yr Uncorrected de Waard-Milliams rate
getCorrosionSeverity() — Low / Medium / High / Very High

Intermediate Results

Method Unit Description
getCO2FugacityBar() bar CO2 fugacity
getCO2FugacityCoefficient() — Fugacity coefficient
getCalculatedPH() — Equilibrium pH of CO2-saturated water
getEffectivePH() — Actual pH if set, otherwise calculated pH
getScalingTemperatureC() °C FeCO3 protective film threshold
getWallShearStressPa() Pa Wall shear stress
getPHCorrectionFactor() — $F_{pH,T}$
getScaleCorrectionFactor() — $F_{scale}$
getFlowCorrectionFactor() — $F_{flow}$
getGlycolCorrectionFactor() — $F_{glycol}$

H2S / Sour Service

Method Unit Description
getCO2PartialPressureBar() bar CO2 partial pressure
getH2SPartialPressureBar() bar H2S partial pressure
isSourService() boolean True if H2S pp > 0.003 bar (NACE MR0175)
getSourSeverityClassification() — Non-sour / Mild / Moderate / Severe

Corrosion Allowance

Method Description
calculateCorrosionAllowance(double designLifeYears) Returns CA in mm (min 1.0 mm per NORSOK M-001)

Severity Classification

Severity Rate (mm/yr)
Low < 0.1
Medium 0.1 – 0.3
High 0.3 – 1.0
Very High > 1.0

Parameter Sweeps

// Temperature sensitivity study
List<Map<String, Object>> tempSweep =
    model.runTemperatureSweep(5.0, 150.0, 30);  // min, max, steps

// Pressure sensitivity study
List<Map<String, Object>> pSweep =
    model.runPressureSweep(10.0, 200.0, 20);

Each point in the returned list contains: temperature/pressure, CO2 fugacity, pH, scaling temperature, baseline rate, corrected rate, and severity.

JSON / Map Output

String json = model.toJson();       // Full JSON report
Map<String, Object> map = model.toMap();  // Map for programmatic access

The output includes:

Java Example

NorsokM506CorrosionRate model = new NorsokM506CorrosionRate();
model.setTemperatureCelsius(80.0);
model.setTotalPressureBara(50.0);
model.setCO2MoleFraction(0.03);
model.setH2SMoleFraction(0.001);
model.setFlowVelocityMs(5.0);
model.setPipeDiameterM(0.254);
model.setLiquidDensityKgM3(1010.0);
model.setLiquidViscosityPas(0.0008);
model.setInhibitorEfficiency(0.80);
model.calculate();

System.out.println("Rate: " + model.getCorrectedCorrosionRate() + " mm/yr");
System.out.println("Severity: " + model.getCorrosionSeverity());
System.out.println("pH: " + model.getCalculatedPH());
System.out.println("Sour: " + model.isSourService());
System.out.println("CA (25yr): " + model.calculateCorrosionAllowance(25.0) + " mm");

Python Example

from neqsim import jneqsim

NorsokM506 = jneqsim.process.corrosion.NorsokM506CorrosionRate

model = NorsokM506()
model.setTemperatureCelsius(80.0)
model.setTotalPressureBara(50.0)
model.setCO2MoleFraction(0.03)
model.setH2SMoleFraction(0.001)
model.setFlowVelocityMs(5.0)
model.setPipeDiameterM(0.254)
model.setInhibitorEfficiency(0.80)
model.calculate()

print(f"Rate: {model.getCorrectedCorrosionRate():.2f} mm/yr")
print(f"Severity: {model.getCorrosionSeverity()}")
print(f"pH: {model.getCalculatedPH():.2f}")
print(f"Sour: {model.isSourService()}")