Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

High corrosion and wear resistant coating produced by plasma discharge in a liquid electrolyte and optimised for magnesium alloys

KERONITE is an environmentally friendly electrolytic oxidation coating for Magnesium. The treatment is an effective substitute to the traditional chromating process. KERONITE is a corrosion resistant, hard ceramic (400 - 600HV), which enables to use Mg in functional applications. Thickness of KERONITE ranges from 10 to 50 microns. The layer is completely uniform and well bonded to the Magnesium substrate.

Coating of magnesium alloy by the KERONITE process involves creation of a plasma discharge around a component immersed in electrolyte that results in oxidation of the component surface as well as elemental co-deposition from the electrolyte solution.

The low concentrated alkali electrolyte does not contain any toxic or aggressive elements and is no more hazardous than water in a domestic washing machine.
The KERONITE layer is the complex oxide ceramic consisting mainly of spinel (MgAl2O4 or MgO-Al2O3). Such composition provides KERONITE with a combination of high hardness and wear resistance together with corrosion resistance and resistance to fretting.

KERONITE on Magnesium Alloys is characterized by following properties:
- High Corrosion resistance: Magnesium alloy AZ91D with KERONITE coating can survive 1000 hours in a salt spray environment without significant visual evidence of corrosion attack.

- Galvanic corrosion: polymer sealed KERONITE reduced galvanic corrosion with stainless steel in saline solution from current density 10-2 A/cm2 for bare magnesium down to 10-11 A/cm{2}.

- High hardness and wear-resistance: microardness of KERONITE on Magnesium ranges from 350 to 600HV (Rc 36 - 55) depending on the alloy.

The KERONITE surface can be used as a matrix for composite coatings, when two coating systems were used in conjunction, in order to create superior properties for the combined coating. The external coating penetrates partly into the porous top layer of KERONITE and partly remains on the surface.

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Reported by

Keronite Ltd
Granta Park, Great Abington
CB1 6GP Cambridge
United Kingdom
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