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Stainless Steel Corrosion


Question:

I have been using hardware made of 303 stainless steel and when exposed to a salt atmosphere, the parts begin to rust. I need to stay with stainless material. Is there another type of stainless steel or a stainless process that will better resist rust?

Answer:

Free machining austenitic stainless type 303 is not as resistant to rusting as the other austenitic grades will be. This is due to the sulfur, selenium or tellurium free machining additives, which will act as sites for corrosion to initiate. Additionally, passivation of type 303 stainless requires different bath chemistry compared to the standard austenitic grades. The austenitic stainless steels, including types 302, 304, and 316 are preferred for salt atmosphere/marine environments. Optimum corrosion resistance can be obtained by specifying a smooth surface finish, thoroughly cleaning the surface and performing a passivation treatment. The passivation treatment consists of immersing the parts in a 30% nitric acid solution which removes any iron contamination on the stainless surface which could serve to nucleate rusting. Passivation will also remove any oils from the machining process to make the part more cosmetically attractive.

We, at Accurate Screw Machine, can manufacture parts in any and all of the stainless steel materials mentioned above, as well as taking care of any of the passivation needs.

If you have questions on these materials, or any other materials your working with, as well as any finishes or finishing processes, please contact our engineering department. They will assist you with any technical issue that may arise. They can be emailed at engineering@accuratescrew.com.