ENVIRO-COAT: ENVIROnmentally assisted, engineered Corrosion prOducts for Aqueous corrosion miTigation

One of the most pertinent threats to successful operations in the energy sector is internal corrosion of carbon steel pipework when transporting high temperature (>120oC) aqueous media. This degradation mechanism is apparent in the nuclear, oil and gas, carbon capture and storage and geothermal industries to name a few. Failure to manage internal pipeline degradation properly results in unexpected failures, leading not only to financial losses, but significant leaks can also have severe environmental consequences.

The most common method of corrosion mitigation for carbon steel pipelines is via the addition of corrosion inhibitors to process fluids. However, such chemicals typically have a poor environmental profile and those which conform to European legislation regarding toxicity and bioaccumulation characteristics typically lack the required efficiency at elevated temperatures to suppress corrosion to acceptable levels. In the context of imidazoline chemistries (one of the most common classes of molecules used in industry) the poor inhibition is attributed to their propensity to undergo hydrolysis into their less efficient pre-cursors. In addition to these challenges, the cost of corrosion inhibitors over the lifetime of a facility can be particularly high. In 2016, the annual expenditure on corrosion inhibitors in Europe was in excess of £2 billion, with power generation and oil and gas sectors occupying the two largest proportions of this share.

It is apparent that a step change is required relating to how internal pipeline corrosion is controlled in high temperature aqueous environments if carbon steel is to continue as the most favourable material of choice in high temperature environments. This proposal focuses on engineering a solution to suppress corrosion which is cost effective and greener for the environment.

The proposal focuses on harnessing the protective properties of corrosion products which naturally form on the internal walls of carbon steel when exposed to high temperature aqueous media. The most commonly observed corrosion product at elevated temperature is magnetite, an iron oxide which possesses unique magnetic and electrical properties. Although magnetite has been shown to provide an effective barrier to uniform corrosion of carbon steel, its electrically conductive nature allows this oxide to support electrochemical reactions which results in localised corrosion occurring through galvanic effects. The intention of this proposal is to identify a method of augmenting the magnetite structure to suppress its electrochemical activity, producing a layer which provides superior protection against both general and localised corrosion compared to conventional corrosion inhibitors.

In order to augment the magnetite layer, a method of co-precipitation in the presence of transition metal ions will be adopted. The hypothesis for this work is that the incorporation of trace amounts of transition metal ions into the crystalline lattice of magnetite (supplied directly via the solution or from within the corroding metal itself) will be sufficient to alter the layers electrochemical activity. The ability of transition metal to modify the chemical and physical properties of magnetite has been demonstrated in other disciplines (e.g. catalyst development). However, such an approach has never been instigated in the context of corrosion management.

By selection of appropriate transition metals which exhibit zero or minimal toxicity at the required concentrations for augmenting magnetite, a 'batch' method of treatment, or superior alloyed carbon steels can be developed, eliminating the requirement for continuous injection of corrosion inhibitors. These approaches will provide more cost effective, efficient and greener alternatives to the deployment of conventional organic corrosion inhibitors.

High temperature aqueous corrosion and its control is generating significant interest from industry. This is largely attributed to the requirement for carbon steel to withstand the transition towards increasingly harsher operating conditions in processes such as oil and gas production, as well as the introduction and growth of newer technologies such as carbon capture and high enthalpy geothermal energy.

During the lifetime of this proposed project, impact will be realised through raised awareness of high temperature corrosion across the energy sector to material and corrosion engineers. This will encompass operators (e.g. BP [Oil and Gas], Shell [Carbon Capture] and United Downs [Geothermal]), material integrity/chemical service companies (e.g. Wood, Schlumberger), but also corrosion consultants (e.g. Element, Intertek) and steel/pipeline producers (e.g. Hesteel group). Collectively, workshops, National Association of Corrosion Engineers (NACE) technical committee meetings, conferences and publications will achieve two targets; (i) promote a behavioural change amongst the aforementioned groups with regards to corrosion control under extreme aqueous conditions by demonstrating doped-magnetite layers are an effective alternative to conventional chemical treatments; (ii) highlight the advantages of dual autoclave systems for relating laboratory data to the field by comparing and publishing results against single vessel systems.

In the medium term, the technical reports/publications developed from the project will be used to introduce and/or update international standards relating to high temperature autoclave testing (specifically TM0171-HD1995-SG), promoting best practice amongst industry. This is particularly important for companies involved in material and corrosion inhibitor evaluation at high temperature, where appropriate assessment for field applications is paramount. Such changes in standards will raise awareness amongst industry, changing how engineers and chemists consider the assessment of materials and chemicals when using autoclaves. It is envisaged that this will, in turn, develop better methodologies to produce more reliable laboratory data, enabling more robust conclusions to be drawn regarding material/chemical performance in the field.

In the long term, the planned publications and reports described in 'Pathways to Impact' will demonstrate that greener alternatives are available for high temperature corrosion control, promoting a change in professional practice/culture for operators, and in particular, chemical vendors and steel manufacturers/pipeline suppliers. The outcomes of the project will influence product development of chemical vendors for high temperature environments, promoting a transition towards greener treatments, but also encouraging the implementation of new technologies/different approaches for corrosion control. The project will also develop new metallurgies for carbon steel, encouraging suppliers to strategically tailor carbon steel metallurgies for specific operating conditions for improved protection. The superior efficiency of these new products will influence corrosion management strategies implemented by operators, generating cost savings by preventing unnecessary downtime. In addition, the reduction in likelihood of failures will have benefits for the environment, preventing leaks where there is the potential to harm wildlife/marine life. The work will also provide increased energy efficiency and security as well as minimising impact on the environment.

The work will provide the opportunity for companies to work with The University of Leeds and Dr Barker to commercialise products for corrosion control. More efficient technologies (formulations and/or steel metallurgies) can be developed which avoid implications in terms of toxicity and bioaccumulation. These products will require less/no synthesis, reducing preparation costs and minimising supply chain issues.