Design of next-generation automotive corrosion protective coatings by improving inhibitor transport properties

Lead Research Organisation: Swansea University
Department Name: College of Engineering


The protective coatings industry is responding to the challenge to find a successful materials substitution for toxic anti-corrosion agents.

Chromium (VI) use has been assigned a "sunset" date of 2019 by the European Union, after which its use will be banned. There is now an urgent need to identify new, environmentally acceptable corrosion inhibitive technologies showing equivalent, or better protective capability.

The collaboration is in conjunction with the automotive coatings company, BASF Automotive, to develop new corrosion inhibitive technologies. The current state of the art technology is partially phosphate-based, and remains limited; this results in significant interest in exploiting the properties of intelligent-release pigments, in which corrosion inhibitive species are stored and only released "on demand" in the presence of aggressive corrosion-inducing agents. Furthermore, there is also a need to improve transport of the inhibitor species from the bulk of the coating, to the areas where they are specifically required (e.g. defects where the underlying metal is exposed). Currently, only a finite quantity of inhibitor originating from the coating in the immediate vicinity of the defect may be available to protect exposed metal.

By introducing long-range percolation networks within the coating, it is thought that enhanced transport of corrosion inhibitor to defect-containing regions can produce significantly more effective corrosion inhibition at the exposed metal, as such providing enhanced efficiency of the technology.

The Research Engineer will:

- Investigate the efficiency of corrosion inhibition at penetrative coating defects using current state of the art phosphate-based pigments and novel smart-release ion-exchange pigments, loaded with various corrosion inhibitive species.

- Carry out a detailed study through variation of discussed groups of pigment loadings within a coating, to evaluate the effect on speed of inhibitor release and subsequent defect 'healing'.

- Assess novel inhibitor delivery systems such as nanotube reservoirs, ion exchange resins and minerals, and conducting polymer networks, as a means of introducing a long-range percolation network for inhibitor pigment within the protective organic coating for delivery to the defect site.

- Evaluate how the long-range transport of inhibitor species from a developed, optimised system influences the mechanism of corrosive-driven organic coating failure i.e. due to de-adhesion originating from anodic undermining and/or cathodic disbondment in the vicinity of a penetrative defect.

The main impetus of the work is to identify and develop next-generation protective coatings for technologically important light alloy surfaces, typically aluminium and possibly magnesium automotive alloy grades, although the best performing technologies may also be applied to the protection of steel. This program will exploit outstanding expertise in advanced electrochemical scanning techniques within the group, coupled with high throughput methodologies to quantify protection efficiency of the coating technology in a systematic fashion, providing mechanistic understandings of the corrosion inhibition processes. Identifying these mechanisms will enable the development of new, more effective corrosion inhibition technology that can be incorporated into organic coating systems.

Planned Impact

The CDT will produce 50 graduates with doctoral level knowledge and research skills focussed on the development and manufacture of functional industrial coatings. Key impact areas are:

- The development of new products and processes to address real scientific challenges existing in industry and to transfer this knowledge into partnering companies. The CDT will enable rapid knowledge transfer between academia and industry due to the co-created projects and co-supervision.
- The creation of knowledge sharing network for partner companies created by the environment of the CDT.
- On average 2-3 publications per RE. Publications in high impact factor journals. The scientific scope of the CDT comprises a mixture of interdisciplinary areas and as such a breadth of knowledge can be generated through the CDT. Examples would include Photovoltaic coatings - Journal of Materials Chemistry A (IF 8.867) and Anti-corrosion Coatings - Corrosion Science (IF 5.245), Progress in Organic Coatings (IF 2.903)
- REs will disseminate knowledge at leading conferences e.g. Materials Research Society (MRS), Meetings of the Electrochemical Society, and through trade associations and Institutes representing the coatings sector.
- A bespoke training package on the formulation, function, use, degradation and end of life that will embed the latest research and will be available to industry partners for employees to attend as CPD and for other PGRs demonstrating added value from the CDT environment.

Wealth Creation
- Value added products and processes created through the CDT will generate benefits for Industrial partners and supply chains helping to build a productive nation.
- Employment of graduates into industry will transfer their knowledge and skills into businesses enabling innovation within these companies.
- Swansea University will support potential spin out companies where appropriate through its dedicated EU funded commercialisation project, Agor IP.

Environment and society
- Functionalised surfaces can potentially improve human health through anti-microbial surfaces for health care infrastructure and treatment of water using photocatalytic coatings.
- Functionalised energy generation coatings will contribute towards national strategies regarding clean and secure energy.
- Responsible research and innovation is an overarching theme of the CDT with materials sustainability, ethics, energy and end of life considered throughout the development of new coatings and processes. Thus, REs will be trained to approach all future problems with this mind set.
- Outreach is a critical element of the training programme (for example, a module delivered by the Ri on public engagement) and our REs will have skills that enable the dissemination of their knowledge to wide audiences thus generating interest in science and engineering and the benefits that investments can bring.

- Highly employable doctoral gradates with a holistic knowledge of functional coatings manufacture who can make an immediate impact in industry or academia.
- The REs will have transferable skills that are pertinent across multiple sectors.
- The CDT will develop ethically aware engineers with sustainability embed throughout their training
- The promotion of equality, diversity and inclusivity within our cohorts through CDT and University wide initiatives.
- The development of alumni networks to grow new opportunities for our CDT and provide REs with mentors.


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Description My project involves investigating the potential of new corrosion inhibitors for the protection of organically coated hot dipped galvanised steel. New corrosion inhibitors have been identified through my research which have shown to be effective at preventing corrosion from occurring. I am primarily looking at the effect of these inhibitors on the coating failure mechanism cathodic delamination, where the coating becomes disbonded from the metal beneath exposing the metal to the environment.

As well as corrosion inhibitors, suitable delivery systems of these inhibitors have been investigated as it is crucial that the inhibitor itself is stored away and can then be released only when needed in the right area. Sparingly soluble salts have been used for the past few decades which involve adding these straight to a coating where they can provide effective corrosion protection. However, these salts are prone to premature leeching from the coating which can lead to reduced corrosion protection and have detrimental effects on the environment. I have looked at using ion-exchange resins as a means to store corrosion inhibitors within the resin which can then remain inside until they come into contact with corrosive media where they are released and can prevent corrosion.

Another means of protection I have looked at which has shown promise, is the use of metal organic frameworks (MOFs) as a means to store and release inhibitors under the right conditions. Initial experiments have shown that the MOFs provide a somewhat effective inhibition by themselves when incorporated into a coating. However, upon trying to store corrosion inhibitors within the MOF, I have had some difficulty in achieving this. Further experiments have to be undertaken to try and understand how these inhibitors can be stored within these frameworks.
Exploitation Route Corrosion protection is such an important area of research at the moment and it is crucial that suitable inhibitors are found that can sustain long term protection on metal substrates. The outcomes of my research will provide industry and academics the understanding of the mechanism at which some of these inhibitors work at preventing corrosion and new delivery systems which haven't been explored by other research groups as of yet.
Sectors Construction,Education,Environment,Manufacturing, including Industrial Biotechology