Influence of Nb Content on Sensitization and Pitting Corrosion of Welded AISI 430 Ferritic Stainless Steel

Influência da Adição de Nb na Sensitização e Corrosão por Pite do Aço Inoxidável Ferrítico AISI 430 Soldado

Abstract

In this work, the effect of Nb addition on sensitization and pitting corrosion of welded AISI 430 ferritic stainless steel subjected to autogenous GTAW was investigated by microstructural characterization and electrochemical techniques. The three distinct regions of welding process, weld metal, heat affected zone and base metal of AISI 430 steel with and without Nb were evaluated. The degree of sensitization was measured by double loop electrochemical potentiodynamic reactivation and pitting corrosion was studied by potentiostatic polarization test. The microstructural analyses reported martensite network in the weld metal and heat affected zone of AISI 430 non stabilized. The electrochemical studies revealed that the highest degree of sensitization and the lowest pitting potential are in the weld metal of AISI 430 without Nb.

Key-words:
Degree of sensitization; Pitting corrosion; Ferritic stainless steel; Nb; GTAW