News Release

Does injection moulding of magnesium need surface coatings?

February 2002

 
Trevor Amos of Poeton Industries, a world leader in surface coating technology, examines the current vogue for magnesium injection moulding and suggests there is still added value potential for coating specialists with experience in the treatment of high value alloys.

The demand from manufacturers in the automotive, telecoms and aerospace industries for lighter, stronger, thinner, more durable components and even more difficult and complicated shapes has highlighted shortcomings in the West's traditional sand and die casting methods of production for metals such as magnesium.

This has led to a growing interest in precision injection moulding of magnesium, a production technology more widely used in the Far East. The high-speed process is based on the principle that, as magnesium approaches melting point a mechanical shearing of the semi-solid metal generates a thixotropic structure that allows it to be injection moulded in the same way as plastic.

Injection moulding is able to produce thinner, denser structures and an excellent finish to very tight tolerances, even on components with complex shapes. And the improvement in surface finish virtually eliminates the need for post-moulding machining.

Combining this injection moulding process with a duplex coating such as Poeton's Apticote Keronite 3000, offers design and production engineers a significant advance in the way magnesium can be used to manufacture a wide range of products previously beyond the scope of traditional casting methods.

For example, Apticote Duplex Coatings add extremely high corrosion and mechanical wear resistance to magnesium's light weight and strength, and can provide aesthetically attractive finishes for consumer products such as mobile phone and computer cases, camera bodies, automotive interior components, etc. Compare this with untreated alloys where the wear rate of magnesium is reduced by a factor of 10 and, as the substrate is very soft, only the lightest loads can be supported.

The properties of the Apticote Keronite 3000 Duplex Coating are already proven, with the coating system being used successfully and extensively on traditionally cast components, even though the surface can be porous.

However, its application with hundreds of thousands of injection moulded components has proved even more impressive, producing a structurally superior product with even higher wear resistant properties, up to 500 hours resistance in salt fog corrosion tests and hardness values up to 600HV can be achieved.

Significant benefits over other coatings include better corrosion protection than any other magnesium treatment process, including other PEOs, more accurate coating and better impact resistance than sprayed ceramics and better abrasion resistance than sprayed coating, anodising or plated coatings. Adding a polymer can also reduce the friction properties of Apticote Keronite 3000 and on purer magnesium alloys, coatings of 60µ thickness or more provide insulation at 1,000 volts DC.

The Apticote 3000 technique can process magnesium components 32 times quicker than aluminium parts with an approximate 10 fold price differential. And there is another bonus from combining the injection moulding process with Apticote Keronite 3000 - both are environmentally friendly, non-toxic processes.

Since the introduction of Keronite and its development as an Apticote process, Poeton has probably gained more experience than any other surface treatment specialist in handling volume production.

To discuss surface treatments for injection moulded parts, sample part processing or technical advice call Poeton Industries now on 01452 300500.

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