Faraday Corrosion Rate & Metal Loss Calculator
Calculate electrochemical corrosion penetration rates (mils/yr & mm/yr), annual steel weight loss, and remaining pipeline wall life from corrosion current density per Faraday’s Law.
Corrosion Current & Surface Area
Pipe Wall Thickness & Retirement Limit
Corrosion Penetration & Wall Life
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Frequently Asked Questions
What is Faraday’s Law of electrochemical corrosion?
Faraday’s Law governs the quantitative relationship between corrosion current and metal loss: the mass of metal dissolved m is directly proportional to the current I, exposure time t, and equivalent weight EW of the metal, divided by Faraday’s constant F (96,485 C/mol): m = (I · t · EW) / F.
What is a "mil per year" (mpy) and what are typical industrial limits?
One mil per year (1 mpy) equals 0.001 inches of metal penetration per year (0.0254 mm/yr). Per NACE SP0775 guidelines, < 1 mpy is considered low/mild corrosion, 1 to 5 mpy is moderate, 5 to 10 mpy is high, and > 10 mpy represents severe aggressive corrosion requiring immediate mitigation.
Why does localized pitting corrode much faster than uniform corrosion?
In pitting corrosion, a tiny anodic holiday (e.g. coating defect) is coupled to a massive cathodic surface area. This extreme area ratio concentrates the entire galvanic corrosion current into a microscopic pit, accelerating local penetration rates by 3 to 10 times the uniform average.