You don't mention maximum temperature, which is very relevant to alloy selection.
Is the service clean; i.e., non-fouling over time?
Corrosion data for mixtures like yours can be hard to come by. Further, contamination can have a multiplying effect on rates.
You are into some fairly expensive options so it is worth doing some testing in the actual fluids and service conditions. That, and/or find out what others in the same industry who do the same thing are using.
The Nickel Development Institute might be able to help.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

maybe a duplex will suits your request but as
ironic metallurgist posted more information is needed.

regards

luis

Perhaps, C276 in a thin walled pipe ?

What is the pressure, flowrate and temperature range ?

https://www.sandmeyersteel.com/images/alloy-276-sp...

MJCronin
Sr. Process Engineer

Normally, copper alloys such as 90/10 are forbidden for use in the presence of sulfides. I don't know that sulfates are particularly corrosive to copper but sulfate reducing bacteria are. Microbial growth may or may not be easy to prevent. I don't know about the corrosive nature of sulfates.

yes maybe Hastelloy C would result.

"Hastelloy C-22 alloy composition has many benefits that help enhance resistance to pitting, crevice corrosion, and stress corrosion cracking. It has excellent resistance to oxidizing aqueous media including wet chlorine and mixtures containing nitric acid or oxidizing acids with chlorine ions."

luis

Temperature first. There is a wide range of materials that could be used.
But like you said the S pretty much rules out Cu and CuNi alloys. The Cl level rules out basic (304/316) SS grades.

You say sulfate, are they really sulfates, or are there other forms (sulfides) present as well?
Are there any other trace contaminates?
What material is the rest of the circuit made of?
What size of line is this (diameter and length)?

Is this for the tubes in the heat exchanger? Who is designing it? If so I presume that they will be small (1/2"-1" diameter) and thin wall (0.028"-0.065") depending on temperature, flow, and pressure.

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P.E. Metallurgy

I concur with some of the previous opinions that you are probably into the category of elite C alloys, especially if there is any significant elevated temperature:
Inconel 686, VDM Alloy 59, Hastelloy C-22, C-2000, C-276
Seamless of course.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

Either be lazy and buy seamless, or write a spec that requires inspection and by the properly made welded tubing and save a lot of money. And then still run the risk of getting incorrectly heat treated seamless product and having failures.

Unless this system is hot it doesn't need a Ni alloy, there are plenty of high performance SS grades that are used on seawater heat exchanger service all of the time, superaustenitic (AL-6XN, 25-6Mo), superferritic (SEC-CURE), and superduplex (Zeron100, 2507) might all be candidates.
At high temps you are moving into Ni alloy range.

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P.E. Metallurgy

EdStainless gives good advice ...

But since the original poster has now abandoned this thread, we will never know the system temperature.

IMHO, always compare the cost of your candidate materials (superaustenitic, superferritic , and superduplex ) to C-276 NI alloy

C-276 came off patent a couple of years and the Chinese supplied tube is being priced very competitively

MJCronin
Sr. Process Engineer

The other option is Tigr2, it is about the same price as SEA-CURE, the 2507 and AL-6XN are about double that price, and the Ni alloys would be about triple that amount.
The issue with Ti is the mechanical weakness, it requires designers that know what they are doing or you end up with a long term headache.
Yes I made a pretty good living off of replacing bad seamless tube with good welded tube. Bad HT is amazingly common, so are people trying to anneal dirty tubes.

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P.E. Metallurgy, consulting work welcomed

EdS,

We are in a period where technical quality of alloys is noticeably declining, and it is causing problems for users who place extra demands on items such as fittings, valves, welding wire, etc. This is not just due to Far East sourcing, but the fact of the poor control of scrap going into electric remelting furnaces.

As you say, heat treatment can be a problem. Far East suppliers seem to think that the list of ingredients is equivalent to the soup, but you also need to know how to cook the soup.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

AS MATERIALS CORROSION ENG, CONSIDERING HASTALLOY IS THE EASIEST OPTION EVER.

PROVIDING MORE INFO WILL SAVE YOU SOME MONEY

You made no mention of pressure or temperature. Without that information, plastic is the obvious solution.

Tug, he said, "This pipe will be utilized in an heat exchanger." Would you still recommend plastic?

Sorry, I missed that line. They'll just need to make the exchanger much larger.