A comparative study of electrochemical corrosion behavior in Laser and TIG welded Ti–5Al–2.5Sn alloy

Abstract

Corrosion behavior of TIG and laser welded Ti–5Al–2.5Sn alloy was compared using different electrochemical techniques. Bead on plate (BoP) configuration was used for welding of 1.6 mm thick Ti–5Al–2.5Sn plates which led to the formation of complete α′ martensitic structure in laser welds and acicular α along with α′ martensite within coarse prior β grains was observed in TIG welds. Potentiodynamic and cyclic polarization were carried out in 5, 7 and 9 M HNO3 to study the effect of concentration on the galvanic corrosion of laser and TIG welded Ti–5Al–2.5Sn. The oxide layer developed after 192 h of immersion in fuming HNO3 was studied using electrochemical impedance spectroscopy (EIS) and SEM. All the samples showed good passivity but different oxidation behavior was observed mainly because of the surface modification after the welding operation. Keywords: Galvanic corrosion, EIS, Laser welding, TIG welding, Ti–5Al–2.5Sn