Patent ID: 8506777

Claim:
An apparatus for measuring localized corrosion comprising: (a) a single test electrode having length L of a metal under investigation, adapted to contact a conductive fluid, and a reference electrode; (b) a temperature sensor in proximity to the single test electrode; (c) an ohmmeter configured for measuring the resistance across the length L of the single test electrode over a time period Δt to give first and second resistance values R 1 and R 2 ; (d) a device configured for calculating corrosion rates from changes in resistance due to corrosion and subtracting them from measurements of R 1 and R 2 ; (e) a device configured for measuring potential difference between the reference electrode and the single test electrode; (f) a computer programmed for determining polarization resistance R p from the relationship: R p = [ B a ⁢ B c ⁢ M ⁢ ⁢ W 2.3 ⁢ ( B a + B c ) · Density · 2 ⁢ F · L 2 ⁢ ρ ] ⁢ Δ ⁢ ⁢ t ⁡ ( R 1 ⁢ R 2 R 2 - R 1 ) ( Eq . ⁢ 1 ) where: B a and B c are Tafel slopes of anodic and cathodic reactions, respectively, obtained separately or from known values, MW is the molecular weight of the metal of the single test electrode, Density being its density, ρ is the specific conductance of the metal, F is Faraday's constant, L 2 is the square of the length of the single test electrode, and R 1 and R 2 are the resistance measurements over time period Δt; and; and (g) the computer programmed for calculating the localized corrosion from V=Rp·I, which device may be the same as or different from the devices in d) and e), where I is current, and where the current is calculated by an electrical resistance (ER) technique.