Understanding the role of thin film pre-treatments on steel surfaces

The interface between a metal substrate and a protective organic coating plays a vital role in determining the long-term anti-corrosion performance of painted metal products. Prior to the application of an organic coating system to protect against corrosion, the metal surface is subjected to a cleaning regime, typically involving exposure to an alkaline environment, followed by a pre-treatment which deposits a thin inorganic film. This in turn provides an inert surface which improves adhesion with organic-based primer coatings, and in certain circumstances, also offers additional active corrosion protection at the metal-organic coating interface. This project forms part of a larger partnership involving BASF Coatings Ltd, in collaboration with Swansea University and Imperial College London, where the main theme will involve furthering the understanding of corrosion-induced failure of protective organic coatings when applied to metal surfaces. The principal focus of this project will be directed towards a fundamental understanding of the influence of the metal surface prior to the application of a corrosion protective organic coating system on durability.

The research will concentrate on two specific areas of interest:
(i) the chemical nature of the cleaned metal surface prior to pre-treatment and how this affects the formation and composition of current state-of-the-art inorganic conversion coatings.
(ii) the influence of the topography and chemical composition of the pre-treated surface on the durability of a corrosion protective organic coating, initially concentrating on a simple model paint system.
The investigation will be carried out using comprehensive in-situ and ex-situ electrochemical characterization by means of Scanning Kelvin Probe (SKP), Scanning Vibrating Electrode Technique (SVET), alongside potentiodynamic and electrochemical impedance spectroscopy methods in the laboratories of the Swansea University corrosion research group. Surface chemical and structural characterization will be carried using a suite of instrumentation including X-ray-photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (XRD), and field emission gun scanning electron microscopy (FEG-SEM).

Project Tasks:
- Investigate the influence of various industry standard chemical cleaning technologies on the surface chemistry of cold-rolled galvanised steel and zinc-magnesium-aluminium (ZMA) alloy coated steel substrates.
- Study the effect of cleaning regimes on the efficiency of thin inorganic film formation using current pre-treatment technologies such as phosphate, zirconate and titanate-based types.
- Investigate the influence of both the cleaned and pre-treated surface on resistance to corrosion-driven failure when overcoated with an organic layer. For steel and galvanised steel surfaces, this will include an evaluation of the organic coating failure via cathodic disbondment and anodic-driven organic coating failure.

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:

Knowledge
- 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.

People
- 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.