Super Duplex SS Time required for natural passivation
Super Duplex SS Time required for natural passivation
(OP)
Dear all,
Does anybody know or has any experience with Super Duplex SS?
Assume that I scrape it or machine it. How long should I wait for the chrome layer to buildup? Is it hours , days or months?
I don't want to put the pipe in service and see any rust!
And passivation is not an option.
Thanks,
Herc
Does anybody know or has any experience with Super Duplex SS?
Assume that I scrape it or machine it. How long should I wait for the chrome layer to buildup? Is it hours , days or months?
I don't want to put the pipe in service and see any rust!
And passivation is not an option.
Thanks,
Herc





RE: Super Duplex SS Time required for natural passivation
The real problem is that if you scrape it with steel then you will embed metal into the surface. The rust is that embedded material corroding not the DSS.
Avoid metal tools and you will be fine.......
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Super Duplex SS Time required for natural passivation
.Any coating to suggest?
Do you know of an article somewhere that explains why it takes seconds?
Some people are pretty adamant saying it takes 2 weeks to repair.
Thanks
RE: Super Duplex SS Time required for natural passivation
Look at HDPE coatings. Heck, pick up truck spray bed liner would work to protect the surfaces.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Super Duplex SS Time required for natural passivation
RE: Super Duplex SS Time required for natural passivation
As long as you don't slide against it it will take a lot of load.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Super Duplex SS Time required for natural passivation
I think that it shall see some sliding...
Will keep that in mind though! thanks
RE: Super Duplex SS Time required for natural passivation
RE: Super Duplex SS Time required for natural passivation
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Super Duplex SS Time required for natural passivation
SS will naturally form a passive chrome oxide layer when exposed to air.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Super Duplex SS Time required for natural passivation
Regarding pickling and passivation...
I thought that pickling was removing the free iron and a small layer of metal from the surface. Agreed? And that happens with some acid + nitric or citric acid.
If what you are saying is true than why are we passivating in just nitric or citric afterwards?
RE: Super Duplex SS Time required for natural passivation
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Super Duplex SS Time required for natural passivation
I understand and agree. So the question remains. Why do we passivate? Is it to enhance the speed or something else of the chrome layer formation? And if yes, that brings me back to my original question. How fast would it selfpassivate.
RE: Super Duplex SS Time required for natural passivation
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Super Duplex SS Time required for natural passivation
RE: Super Duplex SS Time required for natural passivation
However in most manufacturing operations there are cutting, machining, forming, handling steps that may introduce surface issues. Following these with a passivation will give you an optimal surface for corrosion resistance.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Super Duplex SS Time required for natural passivation
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Super Duplex SS Time required for natural passivation
A related question: What is the difference between Passivation ,and electro polishing?
B.E.
The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor
RE: Super Duplex SS Time required for natural passivation
And, it looks pretty.
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Super Duplex SS Time required for natural passivation
RE: Super Duplex SS Time required for natural passivation
h ttp://uk.l inkedin.co m/pub/terr y-roberts/ 28/a9a/a10
RE: Super Duplex SS Time required for natural passivation
I need some help to eliminate porosity in valves of duplex steel (cd3mn).
What's the better deoxidation for this kind of DSS.
A lot of thanks.
RE: Super Duplex SS Time required for natural passivation
Time to passivation.
After extended discussions and a couple of well researched papers this year at NACE I have changed my mind on the issue of time to passivation.
When corrosion testing samples of SS there is a detectable change improvement in corrosion resistance over 72 hours after sample prep. There is no discernible difference between 72hrs and 240hrs, but there is a measurable difference between 0, 24, and 48 hours.
This effect held regardless of the sample prep methods, grinding, blasting, pickling, passivation, and various combinations all showed the effect.
In the real world this not much of a deal since it is rare for parts to go into service in less than 48 hours from finishing.
However in the lab it is a concern. Either test everything ASAP and get more conservative results, or let all samples sit 72hr min and get slightly better results.
I know, this should prob go into another thread. When I get a copy of the paper to read again I will start a thread on this subject.
Ed
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Super Duplex SS Time required for natural passivation
I did some research myself in scientific research and I only found instantaneous formation of the layer in a fraction of a second.
RE: Super Duplex SS Time required for natural passivation
RE: Super Duplex SS Time required for natural passivation
Ed,
I went through 3 years of NACE publications but I didn't find anything specific on the subject of this thread. Do you have any leads ? I got like 20 articles to skim though!
RE: Super Duplex SS Time required for natural passivation
It is from this year.
Ed
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube