African Fusion August 2018

Non-slip plasma coatings

Thermaspray’s Plasma coatings for sticky situations

Thermaspray sales engineer, JohanSquara, describes the Plasma coating process, which involves a thermal spray metal base coating followed by a polymer top coating to offer wear resistance with non-stick properties.

T he excellent release properties of Plasma non-stick coatings from Thermaspray render this surface coating technology ideal for a wide range of applications within industries such as food processing, printing and packaging, paper andpulp, tyre and rub- ber, and conveyor belt manufacturing. These coatings, supplied by Ther- maspray in partnershipwith USA-based Plasma Coatings, combine the advan- tages of thermal spray (metal base) coatings with polymer top coatings to offer benefits of wear resistance, slip and traction. Plasma coatings assist industries in realising substantial cost savings through reduced maintenance and subsequent improved uptime and increased production output. “Twoyearsago,wewereapproached by a bakery that was experiencing prob- lems with dough sticking inside critical areas such as in the bins and dough pumps,” says Johan Squara, sales en- gineer at Thermaspray. The dough is fed by augers through a chute into the bread pans. The bakery, which supplies bread to retail outlets around Gauteng, faced regular downtime and costly halts in production as the dough had to be removed from components and the surfaces thoroughly cleaned. In addition, the on-time delivery of bread to retail stores was being com- promised. “We immediately suggested a Plasma 14000 non-stick coating. The lowcoefficient of friction, excellent non- adhesive properties and long lasting nature of this coating makes it perfectly suited for this type of application.” Thermaspray applied the Plasma 14000 coating to all areas that come into contact with the dough, including augers, dough bins, dough pumps and baking pans. The excellent release and water repelling (hydrophobic) proper- ties of this coating ensures that the dough does not stick and allows it to easily slide off the surfaces of the coated components. Since the application of the coatings in 2016, the bakery, which

runs 24/7, has reported no downtime as a result of dough sticking to surfaces. Squara explains that there is a vast range of different Plasma coatings, which are part of the PTFE (Polytet- rafluoroethylene) family. “A good ex- ample of PTFE is the Teflon coating on frying pans. In addition to being food standard compliant, PTFE is chemically inert, ‘weatherable’, provides excellent electrical insulation andoffers high tem- perature resistance. With the exception of medical plasters, absolutely nothing sticks to these Plasma coatings.” Thermaspray applies Plasma coat- ings to refurbishedcomponentsmeeting OEM standards and in some cases even exceeding OEM standards. This was the casewith the bakery customer, whowas refurbishing an existing plant that oper- ates using older equipment. Squara adds that Thermaspray also coats newcomponents. “Althoughmany OEM components are produced with non-stick coatings, the quality of these coatings does not match our Plasma of- fering. When these coatings eventually wear off, clients approach Thermaspray to recoat the components. Thermaspray offers advice on the correct handling of the coated compo- nents during installation as well as best practice cleaning and maintenance procedures. If the coated components are looked after and well-maintained, correct cleaning procedures are fol- lowed and sharp edges that can scratch the surfaceareavoided, Plasma coatings can substantially extend component life. “In fact,” adds Squara, “if treated correctly, treated components can last a life time.” Plasma coatings are applied to com- ponents at Thermaspray’s facilities as the coatings, which consist of many dif- ferent layers such as primers and bond coats, are applied with a special high- pressure spray gun. The components are then cured in ovens at temperatures of around 300 °C. Squara notes that there are various Plasma coating grades, each

A PTFE-coated bin. Thermaspray offers a vast range of different Plasma coatings from the PTFE family.

requiring different curing temperatures to ensure best results. Other Plasma coatings in the range include traction and release coatings that are used for applications such as paper transfer. Although still presenting non-stick properties, the coated area is able to grip the paper on to the roll and once it has passedover the roll the paper is easily released. This coating is widely used in the tissue paper industry. Testimony to the effectiveness of Plasma coatings is found in studies that show the use of a less expensive grade stainless steel with a Plasma coating outlast an exotic grade of stainless steel without a Plasma coating. Thermaspray is also completing a successful Plasma coating trial at a con- veyor beltmanufacturer. Conveyor belts aremade up of different layers of tightly pressed materials. The belts are manu- factured under extreme pressures and, after release, the material was sticking to the bottomof the press plate, pulling the layers apart. Thermaspray replaced the original plastic coating on the plate, which was proving to be inadequate, with a Plasma coating and the customer is reporting extreme satisfaction with the results.

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August 2018

AFRICAN FUSION