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Publication Date: 02/1/2009
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Cutting Packaging Costs for Molded Plastics

A patented, chrome-free surface treatment process, Keronite® Plasma Electrolytic Oxidation (PEO) technology extends the lifetime of aluminum molds beyond that of steel counterparts while improving heat transfer and throughput rates. The process enables packaging manufacturers to get a rapid return on their tooling investment, increasing productivity and improving the quality of molded parts while holding tight tolerances when molding high volumes.

The treatment process enables molders to reduce tool weight and cost and still get products to market in record time.

The hardness of Keronite depends on the alloy and the thickness of the ceramic layer. It can reach 2000 HV — harder than hard anodizing, steel, glass and most silicon-containing compounds. This, combined with the adhesion and compliance of Keronite, creates outstanding wear-resistance. With a modulus of only ~30 GPa, it is extremely strain tolerant.

While titanium nitride and diamond chrome provide harder surfaces than on aluminum, Keronite provides better dimensional control and superior substrate adhesion.

There are at least 8 good reasons for using aluminum molds treated by Keronite: rapid and relatively low-cost production cycle;mold designs can be altered quickly and cost-effectively, as required; hard but compliant surfaces, providing outstanding wear resistance and ensuring long production life with minimal maintenance and downtime; very thin layers of Keronite ensure dimensional accuracy within tight tolerances for minimal flash and good repeatability; Keronite duplex systems provide a low coefficient of friction and good lubricity with excellent flow and release properties; good abrasion resistance and anti-galling properties, even along vulnerable edges of complex molds or moving parts; inert surface providing effective protection against corrosion or pitting as a result of condensation, gas burn or chemical attack, preventing contamination from oxidation by-products; non-toxic process using no chrome, no acids, no heavy metals and generating no hazardous waste. Wear resistance of Keronite evaluated using pin-on-disk, compared with hard anodizing (Mil-C-8625 type 3) and 5140 steel 50 HRC. Up to seven times more wear resistant than hard anodizing, Keronite is extremely durable, minimizing downtime for maintenance and repairs. Research at the University of Cambridge demonstrates that the stiffness of coating on aluminum is as low as 30 GPa — very unusual for such a hard surface. The combination of extreme hardness and surprising flexibility makes Keronite more mechanically tolerant than other ceramic surfaces. It resists the strain of thermal cycling and molds last longer.

Flexibility gives resilience on impact preventing deformation or cracking. Detached 100µm film can be bent or flattened. In severe deformation, plastic and elastic deformation occurs before failure. During the Keronite process, the exposed surface is progressively converted into a ceramic layer with perfect interface with the substrate, free from any defects. It adheres to the substrate better than any deposited coating such as plasma sprayed ceramics, with reduced risk of surface chipping or flaking.

Keronite grows inwards and outwards from the surface in a controlled way, ensuring repeatability in volume production. The extent of this growth depends upon the alloy, but it will reach 10-40 percent of the total ceramic layer.

Tool designers either allow for this Keronite growth or polish the outer layer back to the original mold dimensions. Either way, tolerances remain tight and dimensions repeatable, making the process ideal for duplicate parts.

Keronite is suitable for complex or textured molds, protecting edges and corners where dip-plating or painting processes fail due to surface tension or "dog-bone" effects. Hard anodizing offers limited protection in these areas because the nature of its growth results in vulnerable wedge-shaped cracks on tight radii. Bare Keronite has surface roughness of approximately 10 percent of the applied layer and very fine-scale surface-connected porosity, ideal for impregnation with topcoats to produce a wear resistant duplex system with the required release properties and/or friction characteristics.

Keronite surfaces can be re-processed should the tool need to be altered, machined or welded at any time. Keronite protects against pitting or corrosion caused by gas burn, acid attack or the chlorides and sulfides generated when certain materials are heated. It also prevents corrosion caused by condensation, enabling the use of water based resins. Without corrosion, there are unlikely to be oxidation by-products contaminating the mold surface, causing problems in sensitive medical or electronics applications. Keronite is used in vacuum forming, blow molding and rotary molding as well as the more aggressive forming tools and resin-bonded sand core molding. In high volume injection molding, tool wear is an expensive problem. Keronite is not only resistant to hot, abrasive plastics and additives such as glass or halogenated flame retardants, but also remains stable under temperature cycling. The company offers a surface treatment service from its own centers of excellence in the UK, the US and China, or will install equipment in those companies wishing to treat their own components or those of their customers.

Contact: Keronite, Inc., 2121 Southtech Drive, Suite 220, Greenwood IN 46143 586-677-2443 or 317-865-1766 fax: 317-865-1828 E-mail: or

Keronite International Ltd, Granta Park, Abington, Cambridge CB21 6GP, UK +44 (0)1223 893222 fax: +44 (0)1223 894222 Web:

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