Process for electropolishing a device made from cobalt-chromium

• US 7,357,854 B1
• Filed: 08/19/2002
• Issued: 04/15/2008
• Est. Priority Date: 08/19/2002
• Status: Active Grant

• Current Assignee: Advanced Cardiovascular Systems Incorporated
• Original Assignee: Advanced Cardiovascular Systems Incorporated
• Inventors: Andreacchi, Anthony S.
• Primary Examiner(s): Tsang-Foster; Susy
• Assistant Examiner(s): Smith; Nicholas A.
• Application Number:
  US10/223,273
• Time in Patent Office: 2,066 Days
• Field of Search: 205640-686, 205/723
• US Class Current: 205/674
• CPC Class Codes: A61F 2/82 Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents stent-grafts for tubular structures of the body other than blood vessels A61F2/04; stent-grafts for blood vessels A61F2/07; instruments specially adapted for placement or removal of stents or stent-grafts A61F2/95; for closing wounds, or holding wounds closed A61B17/04 - A61B17/115; dilators A61M29/00
• CPC Class Codes: A61F 2/91 made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
• CPC Class Codes: C25F 3/16 Polishing

Abstract

The invention is directed to an electropolishing solution for products or devices made from at least in part a cobalt-chromium alloy. The invention is particularly suitable for medical devices or intravascular stents made at least in part of cobalt-chromium. More particularly, the electropolishing process of the invention is particularly suited for use on implantable medical devices, such as stents, due to the biocompatibility of cobalt-chromium alloys. The invention is directed to an improved stent formed from a cobalt-chromium alloy, that possesses an ultrasmooth shiny surface. This invention is also directed to a method of electropolishing such a stent using an acidic electrolytic solution comprising a mixture of 6 parts of about 98% sulfuric acid (H₂SO₄), 1 part of about 37% hydrochloric acid (HCl) and 1 part by of about 85% concentrated phosphoric acid (H₃PO₄) to produce an exceptionally smooth surface.

Claims

1. A method of treating a cobalt-chromium device that includes electropolishing the device in an electrolytic solution, comprising:

combining about 1 part by volume of a first component selected from the group consisting of ethylene glycol, ethylene glycol derivatives and mixtures thereof and at least about 2 parts by volume of a second component that is an acid in solution selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid and mixtures thereof, wherein the first component is a mixture of ethylene glycol, ethylene glycol bisthioglycolate and ethylene glycol diacetate; and

submerging the device in the solution.

2. The method of claim 1, wherein the solution comprises about 1 part by volume of the first component and about 3 parts by volume of the second component, the first component being a mixture of about equal parts by volume of ethylene glycol, ethylene glycol bisthioglycolate and ethylene glycol diacetate and the second component being about 98% by weight concentrated sulfuric acid.

3. The method of claim 1, wherein the solution comprises about 1 part by volume of the first component and about 6 parts by volume of the second component, the first component being a mixture of about equal parts by volume of ethylene glycol, ethylene glycol bisthioglycolate and ethylene glycol diacetate and the second component being a mixture of about 5 parts by volume of 98% by weight concentrated sulfuric acid and about 1 part by volume of 37% by weight hydrochloric acid.

4. The method of claim 1, wherein the solution comprises about 1 part by volume of the first component and about 6 parts by volume of the second component, the first component being a mixture of about equal parts by volume of ethylene glycol, ethylene glycol bisthioglycolate and ethylene glycol diacetate and the second component being a mixture of about 5 parts by volume of 98% by weight concentrated sulfuric acid and about 1 part by volume of 85% by weight phosphoric acid.

5. The method of claim 1, wherein the device is submerged in the solution for a period of time that is proportional to the surface area of the device.

6. The method of claim 1, wherein the electropolished device is a medical device.

7. The method of claim 6, wherein the medical device is a stent.

8. The method of claim 7, wherein the stent is submerged in the solution for a period of time that is proportional to the surface area of the stent.

16. The method of claim 8, wherein the stent is submerged in the solution for a period of time that is proportional to the surface area of the stent.

9. A method of treating a cobalt-chromium medical device that includes electropolishing the device in an electrolytic solution, comprising:

combining about 1 part by volume of a first component selected from the group consisting of ethylene glycol, ethylene glycol derivatives and mixtures thereof and at least about 2 parts by volume of a second component that is an acid in solution, wherein the first component is a mixture of ethylene glycol, ethylene glycol bisthioglycolate and ethylene glycol diacetate; and

submerging the device in the solution.

10. The method of claim 9, wherein the solution comprises about 1 part by volume of the first component and about 3 parts by volume of the second component, the first component being a mixture of about equal parts by volume of ethylene glycol, ethylene glycol bisthioglycolate and ethylene glycol diacetate and the second component being about 98% by weight concentrated sulfuric acid.

11. The method of claim 9, wherein the solution comprises about 1 part by volume of the first component and about 6 parts by volume of the second component, the first component being a mixture of about equal parts by volume of ethylene glycol, ethylene glycol bisthioglycolate and ethylene glycol diacetate and the second component being a mixture of about 5 parts by volume of 98% by weight concentrated sulfuric acid and about 1 part by volume of 37% hydrochloric acid.

12. The method of claim 9, wherein the solution comprises about 1 part by volume of the first component and about 6 parts by volume of the second component, the first component being a mixture of about equal parts by volume of ethylene glycol, ethylene glycol bisthioglycolate and ethylene glycol diacetate and the second component being a mixture of about 5 parts by volume of 98% by weight concentrated sulfuric acid and about 1 part by volume of 85% by weight phosphoric acid.

13. The method of claim 9, wherein the device is submerged in the solution for a period of time that is proportional to the surface area of the device.

14. The method of claim 9, wherein the device is submerged in the solution for a period of time that is proportional to the surface area of the device.

15. The method of claim 9, wherein the medical device is a stent.