Influence of electrode potential on the depth of pitting corrosion in the surface structures of placed steel

Abstract

The paper presents the results of the research that studied how the penetration depth of pitting corrosion in the surface structures of clad steel depends on the steel surface electrode potential. The tests were carried out on the stainless surface of the samples made from steel 09G2S/08X13, which is widely used in production of metal structures for the oil and gas industry due to its necessary mechanical properties and corrosion resistance. The operation process of this steel runs in the technological environment with high corrosivity. The influence of pitting components of the corrosive medium (Сl– и S2O3 2– ions) on the diffusion of oxidants and the development of local processes of destruction of a passive film is shown. It is noted that the maximum influence of the electrode potential on the development of pitting corrosion occurs in the area of secondary passivation. In this case, the depth of pitting can reach 180 μm. Further displacement of the electrode potential of the surface contributes to the phenomenon of transmissivity and leads to the appearance of significant mechanical stresses in the surface structures, causing their cracking. Investigation of surface structures will establish mechanisms for their destruction, and timely implement the necessary anticorrosion measures.

Keywords

• pitting depth
• passive film
• stainless steel
• surface profile
• electrode potential
• polarization curves