EXPERIENCE OF THE CULONOMETRIC ESTIMATION OF THE CORROSION-ACTIVE SURFACE OF AUSTENITIC STEEL IN AN AGGRESSIVE ELECTROLYTE AT CONVERTIBLE DEFORMATION

Abstract

Purpose.The paper investigates the electrochemical behaviour of a complex alloy 05H22AG15N8M2F-Sh (iron 55 %, chromium 20 %, nickel 8 %, manganese 15 %, nitrogen 0.5 %, and sulphur <0.005) in a 3 M HCl solution with static deformation of the variable sign by precision registration of corrosion products in the microgram range of corrosion loss. Methods and Methodology.As shown in the present paper, Coulometric Registration of Corrosion Products (CDCP method) is an effi cient approach to solving the problem of quantitative registration of a trace quantity of a substance for systems with different structural-phase surface conditions. The capabilities of the CDCP method were compared with the traditional (bulk) method to develop a methodology for assessing the effect of the strain sign on the corrosion kinetics of a multiphase alloy. Results.The CDCP method was used to obtain the kinetic dependences of the accumulation of the ions: Fe2+ and Fe3+ corrosion products in the medium and on a compressed and stretched surfaces at different radii of curvature under the conditions of stationary stress. It is shown that the use of the CDCP method is a promising way of signifi cantly expanding the possibilities of corrosion studies of complex corrosion systems. Conclusions. The advantages of the CDCP method for studying the kinetic regularities of a complex alloy corrosion under alternating deformation conditions were achieved. The possibility of conducting selective registration of a trace quantity of stainless steel corrosion products with their combined presence in an aggressive environment was shown. The role of the oxide layer of the products of the metal interaction with the medium were established. According to the results, it can be concluded that it is necessary to study in detail the kinetics of the formation and dissolution of the passivating layer, and, consequently, the feasibility of conducting corrosion tests at an early stage of the corrosion process.

Keywords

• corrosion
• deformation
• coulometry
• volumetry
• surface stress.