Benchmarking the impact of nickel filler addition, weld hardness, environmental pH, and corrosion inhibitors on A333 carbon steel pipe weld corrosion

Abstract

This study addresses the challenge of preferential weld corrosion in ASTM A333 carbon steel piping, investigating the intricate interplay of various factors. The welding process induces microstructural alterations, making affected areas more prone to corrosion, resulting in Preferential Weld Corrosion (PWC). While the addition of 1 % nickel filler shifts the galvanic potential of Weld Metal (WM), its impact on PWC is marginal due to the high rates of its intrinsic corrosion. Notably, nickel filler addition accelerates corrosion in the heat-affected zone (HAZ). In carbon dioxide (CO2) environments, the presence of acetic acid (HAc) intensifies corrosion; yet, the application of morpholine as pH neutralizer effectively counters its effects. Imidazoline based corrosion inhibitor prove successful in PWC mitigation, particularly at elevated pH levels. Furthermore, Post Weld Heat Treatment (PWHT) significantly reduces hardness, aligning with a decrease in corrosion. Of paramount importance, this study not only examining the effects of individual factors, including microstructure, pH adjustment, corrosion inhibitors, and PWHT, but also scrutinizing their combined impacts. The integration of PWHT with pH adjustment and inhibitor injection yields corrosion rates below 0.1 mm/y, ensuring a remarkable 30-year service life even under challenging conditions. This study underscores the necessity of a comprehensive strategy, combining these factors, to effectively manage preferential weld corrosion in carbon steel weldments.