U.K.-based Keronite PLC and Thixomat Inc., Ann Arbor, Mich., have joined forces to produce electrolytic-treated Thixomolded magnesium alloy parts. The Keronite surface treatment reportedly will let magnesium gain a foothold in automotive applications where conventional magnesium alloys are too soft.

Thixomolding is well known for producing near-net shapes that need little finishing — molded parts have smoother surfaces than conventional castings, without flow marks. Surfaces also have lower porosity and fewer defects and, thus, better mechanical properties than die-cast magnesium. That's because Thixomolding eliminates high-velocity turbulence as molten metal enters a die. This prevents oxide and flux inclusions common with conventional casting operations. The process may also promote aluminum enrichment on surfaces, giving greater corrosion resistance than conventional die-cast alloys.

Keronite is a chrome-free immersion process that creates an extremely hard layer on inner and outer surfaces of complex shapes. The process faithfully follows the contours of the substrate surface as it creates a ceramic layer of uniform thickness with high dimensional accuracy. The Keronite thickness can be adjusted to optimize performance. At 400 to 700 HV, Keronite on magnesium has similar hardness to hardanodized aluminium. The process quickly produces a layer typically between 5 and 50 μm at a controllable rate of 1 to 5 μm/min. Magnesium with Keronite coating is an ideal candidate for environmentally friendly, highprecision parts.

A recent EU-funded project called Nanomag tested Keronite on conventionally formed magnesium pistons for small engines used in lawnmowers, motorcycles, and chainsaws. The tests showed Keronitetreated magnesium is as wear resistant as high-silicon cast aluminium. Coupled with Thixomolding this lets magnesium replace aluminium but also steel and plastics in small or lightweight structures that need high precision and corrosion resistance.

Keronite PLC has also formed a partnership with Gramm Oberflaechentechnik of Germany. The pair is developing a cost-effective automated process for selective masking of high-volume components at high speed.