Initial stages of corrosion pits on AISI 1040 steel in sulfide solution analyzed by temporal series micrographs coupled with electrochemical techniques

Corrosion Science Volume: 76 Pages: 27-34 Published: 2013

In situ optical microscopy observation of AISI 1040 steel during the polarization curve, in 31x10-3 mol dm-3 of HS- species in phosphate buffer (pH 7.9). Micrographs obtained at potential of E = Eoc (a), and in E = -645 (b), -556 (c), -544 (d), -525 mV vs. Ag/AgCl/KCl (e). Dotted square focalize just one stable pit with the presence of a cathodic halo more visible in sulfide film (inset).

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Writers: Alexsandro Mendes Zimer; Matheus A.S. De Carra; Emerson Costa Rios; Ernesto Chaves Pereira; Lucia Helena Mascaro

Keywords: A. Low alloy steel; B. Electrochemical calculation; B. Polarization; C. Inclusion; C. Pitting corrosion

Abstract: This work presents a study of the initial instants in the pitting corrosion of AISI 1040 steel, analyzed by temporal series micrographs coupled to an open circuit potential (Eoc) and polarization curves. During the Eoc measurement, the pit induction time and the initial pit growth in MnS inclusions was detected in alkaline sulfide solution. The pit area behavior has two distinct rate of area changes in specific regions directly associated to current slope changes. Finally, it was possible to create a three-dimensional model of the pit depth evolution on the metal, using Faraday’s law and the bullet-shaped geometry.

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