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topic 45296

Duplex Stainless Steel for Drainage

A discussion started in 2001 & continuing through 2017


Q. Hi,

I am a industrialist and want a handbook on stainless steel. Where can I find it?

Chetan Chopra
- Jodhpur, Rajasthan, India

Design Guidelines for the Selection and Use of Stainless Steel


A. Hello Chetan!

One of the best that I've seen for the price (FREE!) is "Design Guidelines for the Selection and Use of Stainless Steel" published by the Nickel Development Institute. Go to nidi.org ^nickelinstitute.org, and order publication 9014.
While you're there, also get a copy of Davidson & Redmond's article on "Practical Guide to using Duplex Stainless Steel", publication 10044, since 9014 doesn't cover the duplex grades well.

If you want something more substantial, a search at Amazon using "stainless steel" should get you enough to satisfy, even neglecting the "stainless steel rat" series of books by Harry Harrison.

Good luck!

lee gearhart
Lee Gearhart

Ed. note, Nov. '17: The Nickel Development Institute has moved to a new domain, and the old domain name leads to a link farm. Publications 9014 and 10044 are still free!

Re-welding duplex stainless steel


Q. If making a re-reweld on duplex s/s should the HAZ of the previous weld be removed prior to making the new weld joint? If yes, why?

Robert C [last name deleted for privacy by Editor]


Q. Hi,
We manufacture stainless steel drainage (channels, gullies, gratings) in grade 304 and grade 316 austenitic stainless and have been doing so for about 30 years now. About 80% of this is internal factory drainage, about 12% is for light commercial applications (kitchens, hospitals, swimming pools, showers), and about 8% is outdoors - on street slot drains, or gullies.

We want to use Duplex Stainless more now and are trying to encourage end clients / architects / building contractors of it's benefits - but I find we are the only company doing this & everybody is afraid to 'jump first'

While I know that a magnet will be attracted to Duplex Stainless, and not to Austenitic Stainless, I can't see how that would render it unsuitable for use in drainage. Firstly for on-street external applications I can see no problem whatsoever, secondly for light commercial applications I don't believe there should be any problem (unless they are flushing away magnet particles!), finally for internal factory applications it should be fine in all Meat/Dairy/Beverage plants but I wouldn't be confident I know enough about what is actually washed away in a pharmaceutical plant.

Duplex is often referred to as being 'magnetic' in literature, but I find this unhelpful as it won't attract other metals, it will just be attracted to a magnet.

Thanks in advance for your comments

Shane Curtin
fabricator employee - Wexford, Ireland

simultaneous (2007)

A. Shane,

If nobody wants your duplex stainless steel, why do you want to introduce it then?
Is it cheaper to manufacture the parts in duplex? Or do you want to sell a cheaper/more expensive product?
What is the problem with your SS 304 and 316 products?

Kind regards,

Marc Quaghebeur
- Brugge, Belgium


A. The duplexes were introduced to give even better corrosion resistance than the austenitics (which are non magnetic). They are much more highly alloyed with approx. 20% Nickel and 25% Chromium, but this makes them proportionally much more expensive.
They tend to be used for applications requiring extreme corrosion resistance, and not light structural or other internal use like yours. So if your end users aren't complaining of corrosion now I don't see the benefit.
There were some early problems with welding I believe, so you should research that.
I wouldn't think the magnetic aspect needs any particular consideration either, since there shouldn't be streams of magnetic particles anyway.
A useful contact in the UK would be Langley Alloys for further info.

Martin Rich
Ship repair - Plymouth, UK


Q. Marc, Martin,
Thanks for your responses - the reason I want to encourage it's use is cost. 304 and 316 have not posed any problems to our customers - it's just that the nickel content has driven their costs through the roof in the last 2 years. We would like to offer the option of duplex but none of our competitors are doing it & our client base is wondering why we are the only ones to do it. They have received some negative comments from our competition - but I really can't find any reason not to use duplex in these situations.

Shane Curtin [returning]
- Wexford, Ireland

simultaneous (2007)

A. The term "Duplex" grade covers a large number of alloys, some very expensive and corrosion resistant, some less expensive and less corrosion resistant. Maybe you could be more specific in which Duplex alloys you are considering. If it is a 2205 type it would be more expensive and more corrosion resistant, for example.

lee kremer
kremer signature
Lee Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
stellar solutions banner


A. Your applications sound like a potential environment for one of the new, low-cost duplex grades like 2003, 2101, etc. I don't see how the magnetic properties will be detrimental either. Your are in the fortunate/unfortunate position of introducing a new technology, and these are the types of issues that all pioneers face. One thing I can recommend is that you read some references about magnetism so that you can explain the difference between magnetically "hard" and "soft" materials. Also, work with your steel supplier to educate your customers about the insane increase in nickel prices, and how the change does not reflect a decrease in performance. Too many cost-reduction efforts are handicapped by the connotation of reduced performance/lower quality, but this represents a technology shift not a reduction. If it's any consolation the entire world of stainless steel production/fabrication/usage is grappling with this fundamental issue of how to address increasing cost due to nickel's increasing price.

Toby Padfield
Automotive module supplier - Michigan


Q. Thank you Lee & Toby,

The Duplex we have been introducing is LDX 2101 (EN 1.4162). We were sure there would be no adverse consequences to using it firstly on external drainage projects - recessed manhole covers which take paved infills, and on-street slot drain, channel drains & so we have been doing this since November. We have not introduced it for internal applications yet though.

Another part of our business is street furniture (park benches, cycle racks, bollards, litter bins) and this is an area where architects have been reluctant to be the first ones to sign off the 'new' material. Here a larger surface area of steel is exposed to the elements and so everyone is afraid to take the risk. As a result we can't tell of our experience for these type of projects. We normally give a grit polished(220/240 grit) or an electropolished finish for these items.

I'm just back from London whereI have been all week. I discussed Duplex with 10 architects, 2 consulting engineers and 2 building contractors - nobody had heard of it (and a couple of these were high profile architect practices). Everybody was quite interested mainly because of cost savings but none of my competitors had ever brought this up.

If I come across as doubtful here in any way, it's just because I have never come across anybody else who has experience in using it.

Shane Curtin [returning]
- Wexford, Ireland


A. Shane
Thanks for posting this question - Working in the slow moving dinosaur of ship repair, I was unaware of the 'lean' duplex stainlesses until now, and have looked around for information on the topic.
You were right, Nickel content for this 2101 - 1.4162 grade is very low at 1.5%, so as long as the corrosion performance is as good as the Outokumpu people say, then I think the combination of cheapness, similar or better corrosion resistance, and high strength makes it a definite important advance in material choice, especially for your constructional/architectural applications.
One cautionary note however, I have some experience of 'new improved' materials sometimes containing a well hidden disadvantage; but time will tell.
Best Regards
Martin Rich

Martin Rich
Ship Repair - Plymouth UK

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Heat Tint Colour Guide to Sea Water Resistance in Duplex or Super Duplex


Q. The project is a desalination plant in Queensland Australia. We are currently undertaking weld trials to establish a WPS to provide effective field welds without internal discolouration by heat tint.

In the event that there is a heat tint what colour is acceptable as a guide to corrosion resistance to sea water?

Can the colour be used as a go no-go test?

References so far have yielded information on heat tints for 316ss but not for SAF 2205 or 2507. The references include: NIDI 11026, AWS 18.2, ASTM ASTM A380 [link is to the practice at TechStreet] .

Experiences from desalination plants would be most helpful in developing a specification that results in a quality job.


Geoffrey D Stone
Engineer - Sydney NSW Australia


A. Hi there,
try electropolishing the stainless steel, you will get a brilliant finish.

Ken Foyn
- Durban, South Africa


Q. I would like to start a research of the properties of the LDX 2101. How can I get this steel?

Jose Sakihama
PUCP - Lima, Peru


A. Hola Jose,

LDX 2101® (EN 1.4162, UNS 32101) is a proprietary 'lean duplex' stainless steel from Outokumpu. Locate their Lima distributor from http://outokumpu.com

What type of research do you intend? First, research the abundant property information available on the Internet.

As mentioned by Martin, 2101 has higher strength than 304/304L (allowing a 25% material weight reduction), better corrosion resistance in many applications and a lower base material cost, so it will likely replace 304/304L in many uses. However, compared to austenitic SS, a duplex stainless is more difficult to cold form, weld and may have high temperature limitations.

Ken Vlach
- Goleta, California
contributor of the year

amadeya42.com honored Ken for his countless carefully
researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work
which the amadeya42 world continues to benefit from.

June 4, 2010

A. I do a lot of design engineering work for Harvey Steel Lintels, who are a niche bespoke steel lintel manufacturer based in Colchester, England.
We spent nearly two years looking at LDX2101 as an alternative to 304, and developing a dedicated new LDX2101 range of lintels.
304 is the construction industry standard for stainless lintels, but the volatile nickel price has really caused us problems - because the price is all over the place, architects have been burnt specifying in cheap time only to build in expensive times and go over budget.
LDX2101 is an ideal alternative for lintels. It is typically slightly more expensive than 304, but because it is over twice as strong, we designed new sections to carry the same loads with less material, resulting in CHEAPER lintels than in 304.
Apart from being price stable, it is also much more corrosion resistant than 304, an added bonus. It also has a more attractive 'brushed' finish, ideal for architectural applications, thanks to mechanical descaling at the mill.
We'll been marketing LDX lintels for around 8 months now, and they're gradually picking up in sales, like you, we have the problem of getting the new material into the market.
Other than to coordinate with 3rd party grade 304 items, we no longer see a need for 304 in lintels (except people still want to stick with the known product). We are aiming to phase 304 out when we can, as LDX2101 is cheaper and a far superior product.
LDX2101 is a no-brainer to replace 304 in most applications.

Guy Seymour
- Colchester, Essex ENGLAND

Duplex 2205 and 2507 particulars? What alloy is good for 15mg/L of residual chlorine?

November 23, 2009

Q. We have had a recent inquiry regarding duplex stainless...

"We are looking for SS with the capacity to handle waters with up to 15 mg/L of chlorine residual.

There is information that
304L will be good for up to 2 mg/L
316L, up to 5 mg/L
This is all we could find with clarification on chlorine numbers and which alloy is suitable for certain chlorine concentration.

We are looking for information on how much chlorine duplex 2205 and 2507 can handle? Is there any testing done to set the limits on how well these different duplex alloys are working with chlorine?"

Cliff Kusch
electropolishing shop owner - North Vancouver, BC, Canada

Welding of Duplex Stainless Steel

November 27, 2017

Q. I am doing my project in pipe manufacturing company. My project title is "Manufacturing of duplex stainless steel pipe by SAW process and problems enrolled with it." As a part of project, I want to know the specific relationship between wire feed speed and travel speed.

Het Dhruv
Student - Gandhidham, Gujarat, India

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