Home /
T.O.C.
FAQs
 
Good
Books
Ref.
Libr.
Advertise
Here
Help
Wanted
Current
Q&A's
Search 🔍
the Site

Chime right in! (no registration req'd)

-----

"Black Oxide's affect on 316 stainless corrosion properties"





February 18, 2010

Does anyone know if black oxide coating alters the corrosion resistance properties of 316 (or 316L, or any other) stainless steel? I'm curious as black oxide contains iron compounds (and iron is not corrosion resistant).

Alvin Vue
Engineering - Minneapolis, Minnesota, USA
^


February 19, 2010

Well you know what that is something that no one has ever asked me and for that matter I have never thought about. The only reason I ever applied black oxide to stainless was to make it look black. I had always assumed that the black finish formed on stainless was the same as that formed on chrome molybdenum steel, magnetite or Fe3O4, but after reading your question and thinking about it I am not even sure if this is the case. My education in this particular case is simply inadequate. I can tell you for a fact that if you took a stainless object that is blued by conventional methods and an un-blued object made of the same material and exposed them to the elements for a period of time. ( I mean the normal climate found in Alberta Canada) The black finish on the blued object would degrade, dull and in some case even pit slightly. The un-blued object would for the most part remain unchanged. In an ocean front environment both objects would suffer although the blued example would suffer much worse. I'm just a gun plumber and I'm drawing on experience here not education. I think we need a chemist !

rod henrickson
Rod Henrickson




gunsmith
Edmonton, Alberta, Canada

^


February 22, 2010

If the coating is properly applied, it shouldn't decrease the corrosion resistance of the stainless. However, I have seen many cases at a particular shop where significant red rust and pitting on the stainless occurred during a 2-hour salt spray exposure. This obviously puzzled us, but after a lengthy investigation, we discovered that the problem came from the use of aluminum oxide blast media that had been contaminated with iron through use. The blast media apparently embedded this contamination which ended up corroding. When we switched to a no-blast pretreatment procedure or to a virgin media pretreatment procedure, the problem went away.

Jon Barrows
Jon Barrows, MSF, EHSSC
Independence, Missouri
^

none
finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread SEARCH for Threads about ... My Topic Not Found: Start NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

 
Jobshops
Capital
Equipment
Chemicals &
Consumables
Consult'g, Train'g
& Software


About/Contact    -    Privacy Policy    -    ©1995-2021 finishing.com, Pine Beach, New Jersey, USA