TWI has decades of experience with a wide range of coatings and surface engineering solutions. Central to many manufacturing processes, coatings and surface engineering is fundamental to the performance and operational longevity of a range of different assets and components across all industry sectors.
Our experts provide a wealth of coatings and surface engineering support to our Industrial Members, including specification design support, surface technology selection, surface preparation, modification and examination, coating application and characterisation, functional assessments, upscaling, simulation, and more.
This expertise has led us to advance processes and deliver solutions across all industry sectors through projects created specifically to meet the needs of specific Industrial Members, joint industry projects which allow interested parties to pool their resources and share the outcomes of our research, and collaborative projects designed to find solutions for wider industry problems and funded by external bodies:
- Cold Spray - Improved Corrosion and Wear Resistant Coatings by Cold Spray
Anti-corrosion and wear resistance are desirable properties that can be provided by certain alloys, but these materials can be costly, meaning that industry looked to coatings to deliver the same outcomes at a fraction of the price. However, corrosion resistant alloy (CRA) coatings, e.g. Ni alloy 625, prepared by thermal spraying were shown to provide greatly inferior corrosion resistance when compared to parent material of the same composition. Even advanced coating techniques such as high velocity oxy-fuel (HVOF) and plasma spraying, produced coatings with interconnecting pathways (due to the presence of micro-scale porosity and oxides); meaning that substrate attack by corrosive media is usually inevitable.
In order to solve this challenge, we created a joint industry project to improve the corrosion and wear resistance of cold sprayed coatings. This was achieved by accelerating fine powders to -1000m.s-1 in a supersonic inert gas jet. On impact with the target surface, the solid particles experience rapid deformation, forming a bond with the substrate and each other to produce a very dense and strong coating.
However, to extend the use of cold spray coatings, we created data on corrosion and wear resistance for a range of cold sprayed materials so that cold spray could be validated for applications such as corrosion resistant vessels, hard-facing, spray-forming and additive manufacturing. In addition, this work investigated the relationship between cold spray particle flight characteristics and coating properties to address these technology gaps.
- High Speed, Low Cost, Hard Chrome Replacement Coating Technologies for Improved Industrial Performance and REACH Compliance
This joint industry project brought together a group of sponsors to test coatings deposited using EHLA (extreme high-speed laser application) and HVAF (high-velocity air fuel) spraying. These processes were benchmarked against hard chrome plating and current alternatives like high velocity oxy-fuel spraying. Through a fundamental understanding of the potential of EHLA and HVAF it was possible to address the industrial drive and applications at the heart of the project, including the relative cost and performance benefits of the new technologies compared to the existing state of the art industrial coatings.
- Advanced Coatings for Offshore Renewable Energy
While much of our work has applications across industry sectors, we do participate in industry-specific projects too – such as the European Commission-funded ‘ACORN’ project, where we worked alongside project partners to develop a new solution to the problem of marine biofouling.
With a focus on static offshore structures such as wind turbine towers and ocean energy generators, the project also developed a corrosion and cavitation resistant coating suitable for tidal energy generators.
- Corrosion Behaviour of PVD and CVD Wear Resistant Coatings in Synthetic Seawater
Another project that investigated wear resistant coatings in marine environments sought to establish the corrosion properties of coatings in conjunction with industrially relevant substrates. The work addressed the need for corrosion performance information for wear resistant coatings in order to allow for a more comprehensive, application-focussed testing approach to assist in future evaluation.
This work involved the testing of wear resistant coatings as applied to nickel alloy 718 substrates. The materials were subjected to immersion testing, crevice corrosion,
and critical pitting temperature.
- Environmentally-Friendly and Durable Oil and Water Repellence Finish on Technical Textiles
Another European Commission-funded collaborative project, ‘TEX-Shield,’ saw us work to develop a novel, multifunctional molecular textile finish that is resistant against oil/grease/powder stains by biological route.
Early water-repellent finishes for fabrics were created with paraffin or wax, which would eventually wash out. These were replaced by PFOS and PFOA perfluorochemicals (PFCs), also known as C8 chemistry. However, these chemicals were found to pose an ecological threat, with C8 chemicals being found in the blood, tissues and foetal-cords of humans, while its bio-persistence and bioaccumulation in the environment has caused significant concerns.
The project saw the creation of a cost effective and environmentally safe finish for textiles, revolutionising the current market, whilst resolving the concerns of the current PFC-C8 based stain-resistant coatings.
- Icelip: Ice-phobic Coating for Aerospace
Icing is an issue faced by industries including aerospace and energy where the build-up of ice contamination can cause difficulties for aircraft, wind turbines and power lines. With regards to aerospace, ice contamination can have a detrimental impact on safety, efficiency, costs, and the environment. Furthermore, in-flight ice accumulation causes airflow disruption and decreases control and performance and large pieces of ice separating during flight can cause problems to engines and impact propellers. Additionally, frozen contaminants can jam control surfaces. Icing contributes to delays, 2.1% of all incidents and 4% of fatal accidents while also increasing drag, fuel consumption and CO2 emissions.
The Icelip project sought to address this issue through the use of ice-phobic coatings that could cope with the demands of the aerospace sector and provide dual functions. The coatings would be formed from ice-repellent multi-functionalised silica nanoparticles bonded strongly to a standard polyurethane clear coat that was already in use in the aerospace sector. The focus of the innovation was the optimisation of a coating developed in previous R&D work by part of the consortium so that it could demonstrate a combination of ice-repellency and durability (TRL 5-6) when tested.
- ‘Pristine’ Anti-Graffiti Project
Our experts were asked to provide assistance in a collaborative project to develop a durable paint repellent coating for long life anti-graffiti protection. Building upon existing expertise in functionalised silica nanoparticles, the Pristine project sought to develop a durable paint-repellent coating that is able to compete with commercially available coatings by offering improved environmental resistance, repellency and easier cleaning characteristics, while using greener materials.
This was achieved by the incorporation of greener novel functional additives into existing coating resins to produce a highly durable hydrophobic and oleophobic coating composed of multiple-functionalised silica nanoparticles. This approach decreased the surface energy of the coating so that it was less than the surface tension of the paint, preventing wetting from occurring.
Graffiti is estimated to cost the UK economy over £1 billion per year, with graffiti vandalism also associated with anti-social behaviour, fly-tipping and littering. This creates a negative perception of areas and encourages further incidents of graffiti vandalism, creating a downward spiral. There are also implications for the graffiti writers themselves, with trespass onto rail lines having led to deaths among graffiti writers.