BLACKENING OF STAINLESS STEEL
We are looking for information on a simple process for blackening of Type 420 stainless steel needles. The blackening should be permanent, corrosion-resistant and medically acceptable. Since the needles are small in size, the method should be capable of processing in bulk.
Q. We are looking for information on a simple process for blackening of Type 420 stainless steel needles. The blackening should be permanent, corrosion-resistant and medically acceptable. Since the needles are small in size, the method should be capable of processing in bulk. M.B.
A. I am aware of one classic formulation that may work for you. The formulation and operating conditions are as follows:
Component/Operating Conditions | Concentration/Range |
Sulfuric acid, | 180 parts |
Water | 200 parts |
Potassium dichromate | 50 parts |
Operating temperature | 210°F |
Two things to keep in mind are: 1) This solution at the temperature specified is rather nasty and must be treated with great care, and 2) Potassium dichromate is a hexavalent chromium compound and may not be acceptable in your facility.
Presumably, your parts could be finished using a basket to hold the needles. If this was my project I would consider using proprietary products. You can find a number of vendors for proprietary products by accessing
www.pfonline.com/plate/index.html and searching the vendor database for Blackening solutions.
Related Content
-
Trivalent Chrome Overview
As the finishing industry begins to move away from the use of hexavalent chromium to trivalent chromium, what factors should finishers consider as they make new investments? Mark Schario, chief technology officer for Columbia Chemical offers a helpful overview of this complicated topic.
-
Products Finishing Reveals 2023 Qualifying Top Shops
Each year PF conducts its Top Shops Benchmarking Survey, offering shops a tool to better understand their overall performance in the industry. The program also recognizes shops that meet a set of criteria to qualify as Top Shops.
-
Choosing and Troubleshooting Copper Electroplating Processes
Learn more on this inexpensive and highly efficient process.