The current portfolio of so-called corrosion resistant alloys (CRAs) in widespread use in the oil and gas industry are not maintenance free, and lead to significant expenditure both in a capital (new and replacement), and operating sense.
Super-duplex stainless steels are somewhat of a default material in the oil and gas industry. However, in spite of being the preferred alloy for seawater application, super-duplex stainless steels remain one of the largest corrosion issues in practice. Welded regions of super-duplex stainless steels consistently underperform in the low temperature heat affected zones (in the vicinity of welds) with respect to localised corrosion.
Similarly, the 13-Cr matensitic stainless steels that are used for subsea pipeline, present their own set of metallurgical issues that renders them prone to maintenance. In all, Woodside uses a variety of CRAs, including austenitic, duplex, martensitic and low Cr variants of stainless steel, and all of them represent durability concerns. Materials engineers at Monash have extensive experience in determination of corrosion as a result of alloys structure and environment, with an unparalleled characterisation capability.
Specific outcomes from corrosion related research upon CRAs will allow researchers to:
- Understand the mechanism of corrosion,
- Predict (and model) corrosion/lifetimes
- Select materials against corrosion – all of which are paramount, and
- Contribute to design and production of new alloys
More demanding environments, or longer life expectancies, demand advanced materials. To date, highly specialised (and expensive) alloys such as Inconel or Hastelloy (high Ni-alloys) are used when performance assurance is required. These alloys however, remain prohibitive in many cases. For example, the cost of subsea infrastructure limits the accessing of small reserves, and when corrosion resistant alloys are expensive this limits business opportunities. To this end, the development of lower cost materials, with appropriate performance (and cost), is an important key to the future.
Monash University has every range of materials production (and testing) at the laboratory scale, and can produce ‘custom’ and ‘fitness for purpose’ materials for trial, using casting, induction melting, arc melting, spark plasma- sintering, powder metallurgy, or even laser processing. Over four decades of advanced alloy development resides within the department, including the past decade on development of stainless light alloys. The opportunity to break the mold with respect to oil and gas materials exists, and whilst it includes metals, it also must extend beyond metals. Composites, advanced polymers, and chemical resistant materials are required to meet the requirements of the most demanding applications.
Coatings presently remain a critical line of defence for corrosion, but also remain one of the largest operating expenses. Coatings are essential for mild steel/carbon steel, and there exists a number of technologies in use already, however they are not perfect. For example, to date, carbon steel is usually used with coatings and liners.
Corrosion is also a critical issue beneath insulation (insulating coatings, which are nominally a rockwool coating). Corrosion under insulation (CUI) is the principal reason for refurbishment of such systems in above ground installations (both onshore and offshore).
There exists immense opportunities for next generation coatings, whereby the following can be achieved:
- Insulation or cladding incorporating conductive elements that renders wet regions protected by an anodic coating component.
- Ultra corrosion resistant surfaces that have been economically (and simply) coated, for example with emerging nano materials, forming a barrier to water.
In recent years, when projects that require significant capital investment are conceived (at the pre- construction phase), durability management forms a key part of the engineering cycle. Design plans are usually supplied to Materials Engineers who undertake a Durability Management Plan (DMP) that involves the materials selection and processing (for example, processing would include aspects such as the welding consumables, etc.).
The DMP is as important as any phase in the construction, and is executed to ensure a structure meets a specified design life; and that materials selection choices are made to meet (or assess if one can meet) the design life. If a design life cannot be met, then ‘planning’ for materials substitution through the design life is considered. Materials selection is a key part of DMP, and contemporary DMP also is applied to refurbishment of capital assets.
Aspects that require careful materials selection include: corrosion resistance, low thermal growth, and no degradation of properties during the design life. It is understood that low thermal growth is a key area in LNG plants, and again, this is a case where established experts in DMP will be able to impart best practice to oil and gas specific applications. Monash staff have extensive experience in DMP, having been involved in several major projects, including the Victorian Desalination plant, which is a modern example of ‘extreme engineering’ and significant capital.
A key aspect of the Woodside Innovation Centre at Monash is innovation. This will stem from what is a truly world-class team, working on technology relevant to Woodside. Key aspects include:
- Access to state of the art facilities, and a pool of global leaders working in the various centres, departments, and campuses of Monash University
- Access to state-of-the-art technologies from other fields including military/defense, aerospace, infrastructure, health, and energy.
- A team of 30 corrosion researchers, who have been developing corrosion resistant alloys and coatings for a variety of industries, including delivering several technologies into the
- Know how in the development of up-scalable graphene.
- A window and constant dialogue with regards to cutting edge technologies and how they can be exploited for enhancing oil and gas.
The above contributes towards a vision for not just reduced maintenance, but the grander visions of corrosion prevention in both new and refurbished parts, with the goal of little to no maintenance. i.e. ‘Prevention’ – overcoming the corrosion threat, and eradicating the consequence.