Avaliação da influência da rugosidade superficial na corrosão de ligas metálicas

Abstract

Corrosion is a major problem that directly impacts the application of metallic materials, especially in coastal environments that have high concentrations of Cl- ions dispersed in the atmosphere. Corrosion is an electrochemical phenomenon directly influenced by the contact area between the metallic material and the corrosive atmosphere. This study proposes to evaluate the impact of the surface roughness that, although invisible to the naked eye, can represent a significant increase in the contact area thus accelerating the corrosive processes. For this, three different metal alloys were used: ASTM A36, ASTM A743 grade CA6NM and ASTM A890 grade 6A immersed in a 0.1M NaCl electrolyte. Surface roughness was created through the surface preparation using 400#, 600# and 1200# grit sandpaper to maintain a regularity of roughness throughout the tests. The tests performed consist of a stabilization of open circuit potential (OCP) of 1h for A36 and 3h for CA6NM and 6A and later analyzes of linear potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). It was possible to observe that the reduction of the surface roughness (obtained by the increase of the sandpaper grit number) had a positive impact on the increase of the corrosion resistance to a border point, in which larger reductions of roughness have little impact.