Progress in Electropolishing of medical nitinol alloys

With the gradual improvement of market requirements for the roughness, gloss and corrosion resistance of metal materials, electrolytic polishing technology, as a precision surface processing technology, has developed rapidly in the field of surface treatment due to its high efficiency, smooth surface of treated samples, and ability to maintain the original properties of materials. At present, there are three types of electrolytic polishing liquid systems that are more popular in the industry: acid-acid system, acid-alcohol system and alcohol-salt system.

Nitinol alloy has unique shape memory, superelasticity, good mechanical properties, friction resistance, corrosion resistance, and biocompatibility, making it an ideal material for the manufacture of vascular stents in medicine, and it has attracted more and more urgent attention in clinical and medical fields. However, if it is not treated, the nitinol stent has a high roughness, and after implantation in the human body, it will produce greater resistance to blood flow there, leading to the formation of blood clots. Therefore, surface treatment of nitinol stents to improve their surface properties has become the key to the preparation of medical alloy stents. In industry, nitinol alloys are generally surface treated by a combination of mechanical polishing and chemical polishing, but the efficiency of mechanical polishing and chemical polishing is low, the process is cumbersome, and the materials with special structures such as brackets are particularly vulnerable to damage. Therefore, the industry usually applies electrolytic polishing technology as the main treatment method to the surface treatment of nitinol alloy brackets.

Electrolytic polishing technology is one of the important processes for surface treatment of metals. This method uses pretreated workpieces as anodes and strong corrosion-resistant materials as cathodes. Stainless steel or nitinol alloys with strong corrosion resistance, lead, etc. are generally used for cathodes in production. It is required to reduce the surface roughness of the material under energized conditions, improve its corrosion resistance and friction resistance, and ultimately obtain a smooth and shiny appearance of the anodizing process. This treatment process has little damage to the bracket and high polishing efficiency. It is a common method for surface treatment of bracket workpieces in production.