Corrosion Rate Calculator | Corrosion Engineering

Quick Answer

The corrosion rate calculator computes corrosion rate (mm/year), corrosion rate (mils per year (mpy)) from the input values you provide.

Result Interpretation

The result shows Corrosion Rate in mm/year and Corrosion Rate in mils per year (mpy), computed directly from the entered inputs using the formula defined for this tool.

Worked Example

Carbon steel in freshwater (30-day exposure)

Given:

weight_loss = 2.34
exposed_area = 20
exposure_time = 720
material_density = 7.85

Expected Result:

corrosion_rate_mm_y = 1.8134
corrosion_rate_mpy = 11.054

The actual numerical result is computed by the Runtime engine using the persisted tool definition. The values shown here come from verified test cases.

Formula / Method

CR = (K × W) / (A × T × ρ)

Where:
• CR = Corrosion Rate (mm/year or mpy)
• K = Constant: 87,600 (mm/y) or 534,000 (mpy) — ASTM G1 standard values (see K Derivation below)
• W = Weight Loss (g) — mass lost by specimen after corrosion product removal
• A = Exposed Area (cm²) — total surface area exposed to the environment
• T = Exposure Time (hours) — duration of test exposure
• ρ = Material Density (g/cm³) — density of the test material

K Derivation:
K Derivation (exact unit conversion):
K_exact(mm/y) = 10 (cm→mm) × 24 (h→day) × 365.25 (day→year) = 87,660
K_exact(mpy) = 1.0×10⁷ × 2.54 / (24 × 365.25) × (1/2.54)³ = 534,189

STANDARD VALUES (per ASTM G1, Table A1.1):
K(mm/y) = 87,600 — ASTM G1 defined constant (rounded from exact 87,660)
K(mpy) = 534,000 — ASTM G1 defined constant (rounded from exact 534,189)

Note: The calculator runtime uses the ASTM G1 standard values K=87,600 and K=534,000.

Corrosion Rate (mm/year); Corrosion Rate (mils per year (mpy)).

Variables

Symbol	Label	Role	Description
weight_loss	Weight Loss	INPUT	Weight Loss
exposed_area	Exposed Area	INPUT	Exposed Area
exposure_time	Exposure Time	INPUT	Exposure Time
material_density	Material Density	INPUT	Material Density
corrosion_rate_mm_y	Corrosion Rate	OUTPUT	Corrosion Rate
corrosion_rate_mpy	Corrosion Rate	OUTPUT	Corrosion Rate

Calculation Steps

Enter the weight loss in g.
Enter the exposed area in cm².
Enter the exposure time in hours.
Enter the material density in g/cm³.
Read the corrosion rate (mm/year) from the results.
Read the corrosion rate (mils per year (mpy)) from the results.

Notes / Limitations

ASSUMPTIONUniform corrosion over the entire exposed area.
ASSUMPTIONWeight loss accurately represents metal loss (corrosion products fully removed per ASTM G1).
ASSUMPTIONExposed area constant throughout test duration.
ASSUMPTIONMaterial density at test temperature approximately equals room-temperature value.
LIMITATIONOnly measures uniform/general corrosion. Does not detect pitting, crevice corrosion, SCC, or intergranular attack.
LIMITATIONRequires corrosion products can be completely removed without base metal loss.
LIMITATIONShort exposure times may give misleading results due to transient effects.

Frequently Asked Questions

What does this calculator calculate?

The Corrosion Rate Calculator estimates Corrosion Rate (mm/year), Corrosion Rate (mils per year (mpy)) based on the input parameters you provide

What units should I use for the inputs?

Enter each value in the units shown next to the input field: Weight Loss (g), Exposed Area (cm²), Exposure Time (hours), Material Density (g/cm³). Make sure all inputs use the specified units for consistent results

How does Weight Loss affect the results?

The weight loss directly affects: Corrosion Rate. Increasing or decreasing this value will change these output values according to the engineering formula

How should I interpret the calculated results?

The calculator provides the following outputs: corrosion rate in mm/year; corrosion rate in mils per year (mpy). Results are computed from the input values using the defined calculation method. Always verify results against project-specific requirements and applicable standards

What assumptions does this calculator use?

This calculator uses verified engineering formulas. Results are approximate and should be validated against site-specific conditions, applicable codes, and professional engineering judgment

When is this calculation useful?

The Corrosion Rate Calculator is useful during preliminary design, feasibility studies, and quick engineering checks in corrosion-rate projects. It helps engineers and designers estimate key parameters before proceeding with detailed analysis

Technical Details

Assumption: Uniform corrosion over the entire exposed area.
Assumption: Weight loss accurately represents metal loss (corrosion products fully removed per ASTM G1).
Assumption: Exposed area constant throughout test duration.
Assumption: Material density at test temperature approximately equals room-temperature value.
Limitation: Only measures uniform/general corrosion. Does not detect pitting, crevice corrosion, SCC, or intergranular attack.
Limitation: Requires corrosion products can be completely removed without base metal loss.
Limitation: Short exposure times may give misleading results due to transient effects.

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