The impact of Ni on the corrosion behavior and microstructure of weld metal fabricated from E8018-G electrodes

Abstract

Due to the importance of the weld metal corrosion, this study aims at the effect of using Ni in weld metals on their corrosion parameters and microstructures. In this regard, the effect of negligible amounts of Ni up to 8.0 wt.% is examined on weld metals made of weld electrodes of the E8018-G type in conditions equal to industrial standards. The corrosion parameters of the weld metals are evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy experiments in a corrosive solution of 3.5% NaCl. The morphology of the weld metals is examined using field emission scanning electron microscopy and optical microscopy. Through evaluating the morphology, corrosion current density (Jcorr), corrosion rate (CR), and polarization resistance (RP) of the weld metals containing different amounts of Ni, it is indicated that Ni plays an important role in creating anti-corrosion properties. The microstructure studies indicate that a weld metal containing 2.91 wt.% Ni is homogeneous, and its major phase is acicular ferrite (AF). The results also show that an optimal amount of 2.91 wt.% Ni in a weld metal provides the highest corrosion resistance in a corrosive solution.