The determination of tafel slopes by an integral method

The mathematical theory of a two-parameter method, based on an integral formulation, for analysing polarization curves is expounded and the basic concepts for searching for the roots of the non-linear system of two equations are developed. This method gives the possibility of computing the Tafel slopes B a and B c and, on the grounds of their knowledge, evaluating I c. Examination of some numerical examples has shown the effectiveness and reliability of this new approach, the convergence of the B an and B cn sequences being very fast when their initial values are inside the convergence radius. The experimental applications concerns the behaviour of Armco iron in H 2SO 4 and H 2SO 4 + Na 2SO 4 solutions at 25°C. The experimental polarization curves were best-fitted using a fourth-degree polynomial, which represents them faithfully over the ΔE interval [−50, 50] mV. Analysis of data generated with the previous polynomial was successful. The comparison of the results obtained using the actual method and NOLI program shows that these two formulations are equivalent, the indications being practically very close, even if the data processing refers to different ΔE intervals. Finally, the evaluation of B a, B c and I c could depend on the choice of the four points ΔE n .