Alloy for Hi T,P in Sulfuric Acid with Chloride

[TEV]

I am looking for a recommendation on an alloy for use in a high temperature, high pressure Sulfuric Acid and Chloride or Sulphate solution. System is tubing and connectors, valves, etc. Conditions are:

Solution 1: 3% H2SO4 + 1% NaCl

Solution 2: 3% H2SO4 + 3% MgSO4 + <1% Al2(SO4)3

Pressure: 1500 psi

Temperature: 250C

Although the concentrations are low, the temperature is the kicker. I'm thinking Hastelloy might stand a chance in this application, but Titanium is not generally recommended for sulfuric acid. Would Incoloy 825 or Inconel 625 have any hope?

 

[BRT549]

Titanium would be good for the salt content, but it would have to be the expensive grade 7 Ti with palladium for the sulfuric acid. Even then there are better choices.

Hastelloy C would be a decent choice. I don't have any corrosion charts for Inconel 625, but the Carpenter book shows Custom Age 625 Plus as a strong performer for both sulfuric and NaCl. Incoloy 825 has only 3% moly, so it may fall victim to chloride stress corrosion. Alloy 20Mo-6 might be a decent choice for a coupon test.

Zirconium is the only metal with excellent resistance in my charts, but it might as well be called &quot;unobtainium&quot; due to the price. It might be hard to find the valves and fittings too, but I'm only guessing. Someone else might be able to fill you in on Zirconium better.

I would recommend coupon testing, since this mixture may have some unexpected properties that can't be predicted by looking at each component individually. This would be a slam dunk for plastic (PVC or PVDF) if not for the temperature.

 

[Metalguy]

I think weak sulfuric acid solutions are reducing rather that oxidizing. I don't know about the other sulfates you have, but if they're non-oxidizing then Hast. B is indicated.

I'd call up the people who make Hast. and ask them.

 

[PVRV]

Hastelloy C276

 

[PVRV]

http://www.super-alloys.com/chembasic.htm

 

[ijaz]

I think Stainless Steel AL-6XN alloy which is a superaustenitic stainless steel is one of the best materials for Sodium Chloride (26%) and Sulfuric Acid (7%) contaminated environments.

Better check with Allegheny Ludium Corporation who developed AL6XN for further details