Medical parts are designed to be used within medical environments and hence are exposed to repeated sterilisation cycles, strictly controlled cleanliness and dimensional tolerance that is near to zero. Therefore, surface treatment is crucial in the design of medical parts.
Electroless Nickel on Complex Instrument Bodies
A uniform layer of material is created by the process of electroless nickel plating. Internal bores, recesses and even threads are all covered evenly and without the variation in thickness associated with the electroplating process. Corrosion is also controlled by the Nickel layer, protecting against sterilization detergent attack.
Hard Anodising for Aluminium Surgical Housings
The oxide layer created during the hard anodising process gives the aluminium surface wear resistance. This surface is suitable for components that are frequently handled and cleaned. The dimension growth is constant and predictable (around 50% of the coating thickness into the surface). Hence this coating can be dimensionally added to a component in design stages. Additionally, a component coated with hard anodising can also be dye coloured for colour coding of instrument sets.
Passivation for Stainless Steel Components
Passivation is used on stainless steel components to remove free iron from the surface to form a strong passive oxide layer to give corrosion resistance. Unlike other Surface Treatments, passivation adds no measurable thickness to the component, making it ideal for use on tight tolerance parts, which are used as surgical instruments or as components that will come into contact with an implant. Material safety guidance for medical devices from the MHRA also sets out the required material properties for medical devices and treatments such as passivation are frequently referred to.
PTFE-Blended Coatings for Moving Parts
PTFE-Blended coatings have been found to be highly effective on moving parts, sliding, pivoting, etc. which are subject to repeated contact with other surfaces and materials. In these types of applications the coating provides low friction with no risk of galling and without the need for lubricants that could form part of a contaminant in a sterile field.
By selecting a surface finish treatment appropriate to the parts’ service conditions (e.g. method of sterilization, material, dimensional tolerance and bio-compatibility), much time and effort can be saved in later design development stages.
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