Oil and gas industry experiences indicate mooring chain corrosion is a major challenge. Observed corrosion rates in the field can be several times higher than the design allowance. In addition, pitting corrosion is not considered in design but can be significant in service. Pre-emptive chain replacements may be required which are typically very costly. In addition to corrosion, some of the other performance factors for mooring chains include strength, wear resistance, toughness and fatigue resistance. Carbon steel is the conventional material currently employed for mooring chains. There are significant incentives to develop new material technologies with improved seawater corrosion and wear performance for mooring chain application.
This paper describes one such new material technology – High Manganese Steel (HMS), and its assessment for mooring chain application. HMS is a family of alloyed steels that, when optimized, can offer improved properties over conventional carbon steel. Several HMS chemistries were manufactured, on which small scale performance evaluation testing and weldability assessments were carried out. Based on the assessments, these custom HMS alloys show promising results in terms of the performance factors required for mooring chain application.