Next generation induction coatings... not just a flash in the pan

With the ever-increasing popularity of induction cookware, Paolo Kirchpfening, global commercialisation manager and Werner Krömmer, business development engineer, manufacturing markets, Linde, look at the latest manufacturing technology to guarantee long-term performance

With the multiple benefits of induction cooktops – from being more energy-efficient than traditional gas or electric hobs, increased safety features, precise temperature control and heat distribution and easy wipe-down surfaces - it is little wonder that the global induction cooktop market is expected to grow by 8.34% and to a value of USD 35.91 billion by 2028.

Induction cooktops (or “hobs”) are becoming increasingly more intelligent and connected. Many now come with features such as WiFi, Bluetooth connectivity, smart sensors and touch control, allowing for automatic pan detection, power management and automatic shut-off which allow users to control and monitor their cooktops remotely. These significant advantages are driving increased adoption of induction technology - as is increased urbanisation, particularly in China and other emerging economies.

Manufacturers are also responding to design trends by offering a variety of colours, finishes, and materials to suit different kitchen styles and preferences.

Digging deeper into induction

The risks of climate change now need little introduction.

We are already starting to live with the impacts of a changing climate on communities, businesses and supply chains. The most recent Intergovernmental Panel on Climate Change (IPCC) report delivered the unnerving news that the world is likely to overshoot the critical 1.5oC mark by 2030, exposing many of us to potentially serious impacts to our way of life.

One way of reducing household energy consumption is to transition to induction cooking which will deliver a 70% reduction in energy consumption, with 90% of the energy produced channelled into the pan itself. Ultimately, that means that food cooks faster using less power.

Safety is also one of the inherent advantages of induction cooking. An integrated Pan Detection System is safer as there is no flame or element to ignite fumes or cause burns – and when pans are removed, the hob stops heating up. Pans and food not only get up to speed faster, but also cool down more rapidly, which makes life easier for both chefs and home cooks, especially when cooking different covers and more creative dishes.

Induction cooking also makes for a cooler environment in the kitchen, as the surface only heats up when a pot or pan is applied, instead of having to keep cooking appliances constantly heated and ready throughout busy service periods. Energy is contained in the pan, which means that the heat doesn’t escape into the surrounding air.

While chefs and home cooks can have the same control over temperature as with gas, induction hobs have an entirely smooth surface, making them easy to clean and maintain, with no little corners or hard to access areas to trap grease or food particles.

Cookware needs to keep pace

Induction cookware is increasing in popularity due to concerns over the use of Teflon as a nonstick coating. While culprit of most concern – PFOA which was linked to cancer – is no longer a constituent in Teflon manufacturing, if Teflon coated pans are overheated, the coating can disintegrate and another chemical (PTFE) released which can be harmful when inhaled or leaches into food.

Another major concern is around the inability to dispose of Teflon coated pans in a truly environmentally safe way once they have reached the end of their lifespan (which can be anywhere from 1-5years). Discarded pans almost always end up in landfill, with the earth absorbing these harmful chemicals.

Most pans today are made of aluminium as it is considerably lighter than heavy cast iron pans and are typically less expensive than those made of stainless steel. However, aluminium pans are non-ferromagnetic and do not work on induction cooktops. To rectify this, aluminium pan manufacturers are bolting ferromagnetic steel plates or coatings to the bottom of the pan.

While induction cookware hobs have made significant leaps and bounds technologywise, conventional production methods for induction coatings of pans (such as brazed induction plates or pressed perforated plates) have not only typically been time and energy consuming, they have been subject to various longer term operational failures. The mechanical bonding between induction plates and the surface of the pan can be weakened over time, resulting in corrosion and making the pan unusable.

An alternative process of literally spraying layers of magnetic materials (for example, ferritic steel) on to the pan base, rather than bonding on an induction plate, not only enables aluminium cookware to be induction-capable, but delivers a whole new quality to induction cookware manufacturing. And with only very thin layers (< 1 mm) of ferritic steel, the weight of the cookware is hardly changed and there is no thermal separation layer between aluminium cookware allowing direct heat transfer without any losses.

Cold spraying: vital to the future of induction cookware

Cold spraying is a material deposition technique where tiny metal particles of between 5 to 50 microns are propelled onto a substrate (for example, an aluminium pan base) using highpressure gases.

The particles, which begin their life at ambient temperatures, are placed in a nitrogen or helium gas stream which is then heated and accelerated through a supersonic nozzle at incredible speeds of between

500 to 1200 meters per second. During the process, the temperature of the metal powder remains far below its melting point, ensuring the metal particles stay in their solid stage, so retain their unique properties and remain oxidation resistant. The coating created via this process is ductile which also prevents any risk of embrittlement under stress.

Due to the high temperatures required (up to 1,100°C) within the gas stream, the manufacturing of coated products is heavily dependent on a number of factors, including the supply of high purity gases and a stable and reliable gas flow with minimal pressure variation – all of which must be within a specified temperature range. Rapid process parameter changes can damage both the gas heater and the nozzle at the tip of the spray gun – so, a constant, reliable pressure is needed to ensure a smooth gas flow which will ultimately influence the coating quality. Any fluctuations can potentially have an impact on delivering a uniform coating and ultimately a negative effect on overall product quality.

In collaboration with German cold spraying technology firm, Impact Innovations, Linde has developed the LINSPRAY® Connect system to ensure the delivery of a reliable, stable and high-quality gas flow with minimal variation.

For the first time, the innovative system enables the kitchenware manufacturers to monitor such process parameters as pressure, temperature and filling levels of the nitrogen tank. It also has the capability to automatically send error messages in real time and can switch to an emergency gas supply or activate a safe shut-down of the system in case of incidents. And production volumes can easily be increased or decreased as required.

Such enhanced capabilities will not only enable thinner coating layers while still retaining long-lasting corrosion resistance, but will also reduce production downtime – and error notifications will allow for proactive, preventative maintenance, reducing the instances of rejects and any rework required.

With not only professional chefs, but home cooks advocating induction hobs and cookware, we can expect a more energy-efficient and environmentally way of cooking in the future.