Selection of Filler Materials to Minimize Preferential Weld Corrosion in Pipeline Steels

Abstract

Preferential weld corrosion (PWC) has long been a problem in the oil and gas industry for pipelines used in process facilities, seawater injection, produced water service, offshore platforms, and downhole production systems. This paper reviews recent PWC field failures in light of mitigation guidelines from existing literature. Environmental effects take precedence over chemical composition and microstructure in determining PWC susceptibility. Therefore, the primary approach to minimize PWC is continuous corrosion inhibition. The ideal PWC prevention method would be the use of autogenous welds or welds made with matching consumables. However, this is not a practical option in the field where most pipelines are typically made from carbon-manganese steels with broad chemical compositions, thereby making them susceptible to PWC. The feasible alternative is to use filler materials with strict compositional control vis-à-vis the following elements: nickel, silicon and chromium. In addition, increased preheat and high heat input welding processes should be employed to minimize PWC susceptibility.

Global and Local Corrosion of Welded Joints of High-Strength Low-Alloy Automotive Steel

“…Such heterogeneous surface triggers the susceptibility to galvanic corrosion in the welded joint. Galvanic effects between WM, HAZ and BM may lead to preferential weld corrosion (PWC), contributing to mechanical failures and reduction in the lifetime of the component [9]. Preferential weld corrosion must be avoided because if the weld is preferentially dissolved, corrosion will be enhanced at the anodic zone by the unfavourable surface area ratio (e.g.…”

“…(small anodic weld area) / (large cathodic base metal area)). PWC of iron-based alloys is usually controlled by using filler materials with the addition of nobler elements such as nickel, molybdenum, copper, or corrosion resistant elements such as aluminium, chromium and vanadium, responsible for decreasing the corrosion rate [9,10].…”