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Magnesium's combination of low weight, biodegradability, and favourable mechanical properties make it an ideal material for a biodegradable orthopaedic implant. However, current magnesium-based materials degrade too quickly to be used. In this work, bioceramic–polymer composite coatings were applied to magnesium in an attempt to improve their corrosion resistance.
The coatings were characterised and subjected to mechanical tests and qualitative corrosion tests. All of the coatings provided some resistance to corrosion, however, due to gas evolution (a by-product of magnesium corrosion), the coatings blister and crack, allowing corrosion to increase.
The adhesion strength of the coating was seen to correlate with the time until cracking failure (during the corrosion test), which indicates that adhesion strength must be increased in order to provide corrosion protection for a suitable time period.
The bioceramic–polymer composite coatings had a lower adhesion strength compared to the polymer only coating, due to poor bonding between the bioceramic layer and the magnesium substrate. This decreased adhesion strength leads to cracking failure occurring earlier during the corrosion test, indicating worse performance.
In order to improve mechanical and corrosion properties of this method, work needs to be done on strengthening the bonding between the bioceramic layer and the magnesium substrate.
•Polymer–bioceramic composite coatings were applied to magnesium.•The mechanical properties and corrosion resistance of the coatings were studied.•The adhesion strength of the coating was found to correlate with the time until coating failure by cracking.•The bioceramic interlayer decreased both the mechanical properties and corrosion resistance.•A failure mechanism for the composite coatings is proposed.