On the surface — uses of surface engineering
David Rickerby, Head of Surface Engineering at Rolls-Royce plc, Derby, UK, introduces everyday uses of surface engineering.
The broad definition of surface engineering – the design of a composite system (coating plus substrate) that provides a performance that cannot be achieved by either the coating or substrate in isolation – coined in the UK in the 1970s, encompasses diverse applications including simple domestic items such as toothbrushes, food packaging, building design and textiles.
Shavers and toothbrushes feature an engineered handle with an elastomer coating to provide a secure grip, better control, and a design that is elegant and highly functional. Bathroom fittings are commonly duplex nickel and chromium electroplated onto metal or plastics, resulting in a pleasing appearance with enhanced durability. Gold plating and black finishes from ruthenium are also available.
Cookers have a high temperature paint finish, which may be vitreous enamelled to protect from heat and aid cleaning. Cast iron cookware can also be enamelled to unite the heat distribution and retention properties of cast iron with a non-reactive, low-stick surface. For those of us who hate washing up, Teflon (polytetrafluoroethylene) coatings make pots easier to clean.
The food we consume is packaged in a wide variety of ways to protect, carry, identify and merchandise the product. Surface engineering is a key driver in the development of improved packaging concepts that reduce the amount of packaging and waste produced, as well as raw material use. In future, printed electronics in food packaging will help sell the products and carry key consumer information, such as how fresh the product is and its environmental impact. Manufacturers will use smart packaging to track storage conditions and receive distribution information. The energy to power the device will be generated from a printed battery device on the package.
On the road
Many of our modes of transport are improved by surface engineering. For example, to minimise the total lifecycle energy consumption of motor vehicles, coatings are applied to reduce rolling and frictional losses within mechanical assemblies and to extend component lifetimes. Most modern diesel fuel injection systems employ low friction, carbon-based coatings to prevent seizure. This technology is likely to migrate to other engine components to achieve future efficiency, emission control and lifetime targets.
To overcome corrosion problems that once plagued the car industry, body parts are plated with zinc alloys and chromate treatments, and are painted in complex systems of phosphate pre-treatment, primer, body coat and clear lacquer.
The environmental impact of transport is reduced by the use of catalytic converters that depend on platinum group metals (PGMs) to catalyse the breakdown of toxic combustion products into less harmful emissions. By optimising the core element of the catalyst, washcoats which greatly increase the surface area for catalytic activity, the performance of catalytic converters has been enhanced and the use of expensive PGMs reduced by surface engineering.
About 40% of the energy used in the developed world is for buildings – be it heating, cooling or lighting. Surface engineering offers the ability to control the flow of light and heat through glazing systems, significantly reducing energy consumption while at the same time self-cleaning.
Fire protective coatings are used to protect residential and office buildings. Intumescent coatings provide passive fire protection by expanding on exposure to heat to form a durable, adherent fire-resistant foam layer. They have a paint-like quality that offers architects scope to deliver aesthetic designs with exposed steelwork.
On exterior surfaces of modern buildings, coated steel products virtually eliminate the need to repaint for 40 years, saving time and money. To further reduce environmental impact, photovoltaics offer the potential to incorporate solar electricity generation into the fabric of buildings, starting with its architectural design. Traditional silicon photovoltaics are applied to buildings, and their use could be extended to windows and façades by organic photovoltaics – solar cells made from plastic – which are approaching commercial applications. Both options are only possible by using surface engineering.
Inside the office, surface engineering is key to the manufacture of high quality, low-cost consumer products and also protecting these from environmental factors such as moisture and contamination.
Modern storage media, such as CDs and flash drives, make storage of data much easier. In the case of a CD, a thin layer of aluminium is applied to the surface to make it reflective, which is then protected by a spin-coated lacquer.
The inside of a desk printer has a number of hard coatings on the rollers to prevent abrasive wear and atmospheric corrosion. The printing media are specially coated to control the movement of ink on the surface, and the quantity of remaining ink in the cartridge is monitored by a tiny printed circuit board. For those who prefer the personal approach, your pen may be plated in all sorts of metallic finishes, or may be ‘soft feel’, as with the toothbrush.
Tokens used for drinks machines, found in many workplaces, will be nickel plated steel. In the UK we now have copper plated one and two pence coins, while in other countries nickel plated steel is also used for ‘silver’ coins.
Wherever we are, we can listen to a range of music on MP3 players, the aesthetics of which are improved by the choice of coloured cases produced by anodising of the aluminium to produce a porous layer of aluminium oxide. This surface readily absorbs dyes to give the required finish that is then sealed to increase corrosion resistance and dye retention.
In the event of rain, modern fabrics can be surface engineered to display stay-dry/clean characteristics. Nanotechnology is used to coat the fibres to create the ‘lotus leaf’ effect seen in nature, and, on this hydrophobic surface liquid cannot be soaked up by the fibres and stains are easily removed.
Next time you read your copy of Materials World, reflect on the number of articles relating to surface engineering and ask – what can surface engineering do for me?
IOM3 Surface Engineering Division