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The application of the transform of Kramers‐ Kronig for computing the polarization resistance
Author(s) -
Rocchini G.
Publication year - 1998
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/(sici)1521-4176(199810)49:10<764::aid-maco764>3.0.co;2-d
Subject(s) - kramers–kronig relations , transformation (genetics) , mathematics , interval (graph theory) , mathematical analysis , electrical impedance , polarization (electrochemistry) , function (biology) , analytical chemistry (journal) , thermodynamics , chemistry , physics , optics , refractive index , combinatorics , quantum mechanics , biochemistry , chromatography , evolutionary biology , biology , gene
Some general considerations on the use of the Kramers‐Kronig transform for computing the real and imaginary parts of the electrode impedance Z(ω) are given and the relationship between R p and Zr(0) is established by considering a simple electric network. Experimental applications concern the behaviour of iron in 5 wt% HCl solutions, containing a specific inhibitor for this environment with concentration values ranging from 0.1 to 3.0 g/kg, at temperatures of 65, 75, 80 and 90°C. Electrode impedance determinations were performed over the [0.08, 2 × 10 4 ] Hz frequency interval under current control. The values of R s were usually determined by processing experimental data belonging to the [0.08, 2 × 10 4 ] Hz frequency interval. The values of R p , based on the use of the first Kramers‐Kronig relation between Z r (ω) and Z i (ω), were computed using the D01GAF subroutine of the NAG library. The accuracy of this procedure was verified by comparing the experimental and computed values of Z r (ω). Comparison of the two sets of values of Z r (ω) confirmed that the use of the Kramers‐Kronig transform was pertinent to analyse experimental data because the reproduction of all examined experimental data was rather faithful over the [0.08, 2 × 10 4 ] Hz frequency interval. At last, the first Kramers‐Kronig relation provide a valid mathematical tool to compute the correct magnitude order of R p as a function of inhibitor concentration.