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Sustainable Organic Coatings for Corrosion Protection

Periodic Reporting for period 2 - SUSTICOAT (Sustainable Organic Coatings for Corrosion Protection)

Reporting period: 2018-09-01 to 2020-08-31

Organic coatings extend the lifetime of major metallic assets at a fraction of the cost or environmental impact of either accepting corrosion resulting in shorter asset lifetimes, requiring more frequent replacement, or using more corrosion resistant alloys which are more expensive and may also use less environmentally friendly elements. However, many of the current range of organic coatings are based on materials whose use is being restricted due to legislation and / or have a limited and often unpredictable service lifetime. The limited lifetime of organic coatings in environments from mild to extreme, necessitates more frequent recoating than optimal, often in challenging environments, such as oil rigs, tall buildings, aircraft etc., with unavoidable safety and environmental concerns.

Organic coatings for metals for architectural, transportation, industrial and domestic uses represent a European market of over €10 billion. The future competitiveness of European organic coatings for corrosion protection is based on product quality, product differentiation, cost, line versatility and environmental compliance.

SUSTICOAT delivered a research and training programme focused on state of the art characterisation, modelling and formulation of organic coatings for corrosion protection to maintain Europe’s competitiveness.

The specific scientific objectives in SUSTICOAT were to:
• Develop fundamental understanding using state of the art characterisation and modelling techniques of the formation and evolution of the pore network in commercial organic coatings, for a range of applications.
• Identify common physical phenomena in the formation, aging and properties of different coatings (solvent-based, water-based, and powder-based) to enhance the ability to predict their performance.
• Provide a link between coating characterisation, formulation and product performance applicable to a range of applications.

SUSTICOAT made the connection between the scientific understanding and the production of commercial organic coatings, while dealing with the complex issues faced when translating scientific concepts into industrial products.

SUSTICOAT’s research and training programmes covered TRL 4-7 (prototype demonstration in operational environment), provided a unique opportunity for training researchers in applied problems and advanced the knowledge and understanding of coatings for corrosion protection at high TRLs.
SUSTICOAT has carried out work which is being exploited to develop more sustainable coatings:
- Chromate is both very effective as an active corrosion inhibitor and very toxic to humans. The work of ESRs 1 and 2, focused on chromate-free replacement technology, has provided new knowledge to enable chromate-free coatings to be produced with improved corrosion protection. ESR1 elucidated the role of corrosion inhibitor particle size on both short and long term corrosion protection. ESR2 was able to determine the role the polymeric binder plays in allowing chromate-free coatings to function effectively. The understanding developed by both ESRs is having direct impact on the development new chromate-free coatings.
- Waterborne coatings are an attractive approach for more sustainable coatings. However, waterborne coatings require the use of additives which can undermine the ultimate performance for challenging applications such as corrosion protection. ESR3’s work has shown that it is possible to overcome the limitations of additives through a detailed understanding of the function of specific additives from manufacture to ultimate corrosion protection.
- Epoxy coatings based on bis-phenol-A (BPA) have provided excellent protection to both food and metal can for decades, however legislation now requires that BPA is no longer used – BPA non-intent coatings. Metal packaging coatings require a wide range of properties on top of excellent metal protection, they need to be resistant to a wide range of foods and drinks, while also being flexible to cope with the can manufacturing process. ESR5 through studying the microstructure of both chemically resistant and flexible BPAni coatings has developed a phase map, allowing the properties of different formulations of BPAni coatings to be predicted.
- The need for long term corrosion protection results in long term testing being necessary before a new coating can be introduced. This need for long term testing is one of the reasons why changes of raw materials in corrosion protection coatings has historically taken decades. ESR4 carried out a detailed study of tests carried out over 5 years of exposure of coatings to determine whether long term failure could be predicted short term test results. While the work did not identify a substitute for long term failure, it does propose a methodology which will allow failing materials to identified at short times than current test analysis allows. The work also showed how current testing is limited by the very wide range of results seen with what are thought to be identical samples.

The results are being used in AkzoNobel's coating development, testing and research, as well as feeding into further collaborative research (SusCoRD).

The scientific outputs of SUSTICOAT were disseminated at the Royal Society of Chemistry’s Formulation Science and Technology Interest Group meeting “Formulating Functional Films and Coatings III” on 19th August 2020, presentations are openly available on the site as both pdfs and recordings – https://www.formulation.org.uk/fffc. The ESRs are currently completing their theses and writing a range of scientific publications.
SUSTICOAT has advanced the state of the art of sustainable organic coatings, through the exploitation of its output within AkzoNobel and further academic collaborations. The scientific outputs have been widely shared through conferences and publications are being written.

The training of the ESRs has been completed, with PhD training, industrial training, practical research and development experience.

The ESRs learnt on the job, in a specialist research environment equipped with the latest technology. Attendance in and active contribution to training programmes, network events and conferences added to their knowledge. In addition, collaborations developed by the researchers during the project have enabled them to develop an international network which they can sustain beyond the duration of the project, leading to opportunities to develop new research projects.

Two of the ESRs have joined AkzoNobel’s Expertise Center Corrosion in the Netherlands to carry out application led research on corrosion protection coatings. One of the ESRs has joined the world’s largest materials technology company as a materials engineer supporting the installation of large infrastructure projects where coatings are widely used. One ESR is looking for suitable academic opportunities in the area of polymers and one ESR is building on experience gained during SUSTICOAT to enter scientific software engineering.

The project website can be found at: https://susticoat.wixsite.com/susticoat.