Summary for stainless steel coating Discussion
Coating for 3xx stainless steel is discussed as a way to reduce corrosion that could contribute to stress corrosion cracking in welded chambers exposed to steam. Brian Devendorf asked for a post-weld coating that could be applied evenly and inspected visually, and suggested an electrostatic coating. Bob Robert J. Dykhouse recommended looking into a silicon oxide coating deposited by PECVD, saying it adheres well to stainless, acts as a moisture barrier, and has been used on scalpel blades that undergo repeated steam sterilization. Ed Bayha offered electropolishing as another option, noting that while it is not a coating in the usual sense, it creates a corrosion-resistant oxide layer on 300 series stainless. Larry Hanke then questioned what electropolishing actually adds, referring to terms like chrome enrichment and ultrapure/ultraclean surfaces. The thread does not settle on one definitive answer, but points to PECVD silicon oxide or electropolishing as possible approaches.
Q. Hello–
I am looking for a coating for 3 series stainless steel that will prevent the corrosion that can lead to stress corrosion cracking.
The surfaces that must be protected are welded together in chambers and exposed to a 15 psi steam flow at a maximum flow of 8000 pounds/hr.
I am guessing some sort of electrostatic coating would be best (to ensure a consistent, even coat), as the coating will need to be applied after welding, and visual inspection of the application.
Any and all comments are greatly appreciated!
Brian Devendorf
1996
A. Look into a silicon oxide coating which adheres well to stainless and is a moisture barrier. We have coated scalpel blades which must withstand repeated steam sterilizations. It might do what you need. It is deposited in a PECVD (Plasma Enhanced Chemical Vapor Deposition) process.
Bob
Robert J. Dykhouse
– Corona, California
A. Have you considered electropolishing? Electropolishing is not exactly a “coating” in the usual sense, but it creates a corrosion resistant oxide layer on Type 300 series stainless steels.
Ed Bayha
Metal Coating Process Corporation – Charlotte, North Carolina
Ed,
What is the “corrosion resistant oxide layer” that electropolishing will add to stainless?
I heard of “chrome enrichment layer”, “Ultrapure” and “Ultraclean” when electropolishing is used on stainless.
Type 300’s stainless is suppose to have a self-oxidation layer (results of the elements in the alloy) that will protect the material from corrosion (when the surface is kept clean). What/how does electropolishing add to stainless that promotes the “corrosion resistant” or “chrome enrichment” of the based alloy?
Regards,
Michael Liu Taylor
specialty stainless steel distributor – Dallas, Texas
books by
Donald Mattox …
“Handbook of Physical Vapor Deposition (PVD) Processing” (2010)
on
AbeBooks
or
eBay
or
The Foundations of Vacuum Coating Technology (2018)
on
AbeBooks
or
eBay
or
(affil link)
A. The thickness of the oxide layer that is formed on stainless steel can be made thicker than the natural oxide by heating is very dry air (-100 °C dew point) to 500 °C. This is a technique for passivating the ID of stainless steel tubing in the semiconductor industry.
Donald M. Mattox
Society of Vacuum Coaters
Albuquerque, New Mexico
Donald is the author of:
“Handbook of Physical Vapor Deposition (PVD) Processing” (2010) [on
AbeBooks
or
eBay
or
Amazon affil links]
and
“The Foundations of Vacuum Coating Technology” (2018)
on
AbeBooks
or
eBay
or
Amazon affil links]
A. Brian, I wonder if a layer of hard nickel plate (electro or electroless) or hard chrome will solve your problem.
Mandar Sunthankar
– Fort Collins, Colorado
A. The passivation condition that is attained on stainless steels from simple atmospheric exposure, chemical passivation, electroplating, or other processing will minimize the potential for general corrosion, but will not prevent stress corrosion cracking.
The original post does not indicate so, but I suspect that the proposed service environment may include chlorides. stress corrosion cracking by chlorides can be prevented only be a coating that provides a complete barrier to to moisture, such as that suggested in the first reply.
Is there a reason for using stainless steel if the surface must be coated anyway? Would a steel vessel work just as well and be cheaper? Steel might corrode at defects in the coating, but would not be susceptible to stress corrosion cracking. Pinholes in the steel would eventually leak – cracks in the stainless steel could lead to a catastrophic rupture. Alternatively, duplex stainless steels and higher nickel alloys are much less susceptible to stress corrosion than the 300 series alloys.
Larry Hanke
Minneapolis, Minnesota