Authoritative Answers, Fun, & Aloha -- no cost, no passwords, no popups
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Home /
Site 🔍
pub     mobile?
Metal finishing Q&As since 1989


Use of Stainless Steel for Concentrated Sulfuric Acid (98%)

Q. One of our clients in Pakistan is having difficulty with sulfuric acid piping. Please note that 98% sulfuric acid is used for DAP production. They intend to replace existing CS piping with stainless steel either 304L or 316L due to frequent leakage problems. Please recommend the suitable SS material for concentrated sulfuric acid service for ambient temperature. Can SS-304L can be safely used?

Muhammad Javed Akhtar
- Copenhagen, Denmark

simultaneous replies 2001

A. Hi Muhammad

If one looks at corrosion charts, then either 304 or 316 s.s. 'seems' to be just OK ... but what about the welds? That would certainly concern me.

Further, is the data given accurate for all operations? If the concentrations dip to around the 50% mark, then s.s. gets attacked very quickly.

If, by chance, your piping has a high spot (i.e., it is not sloping down everywhere) where the air could remain and, in time, the acid concentration could drop, then there's a chance you could have a failure. Example ... 93% sulfuric using mild steel piping from a M.S. storage tank in a Toronto battery plant. Failure. Acid all over the roof. Had they in that case used PVC pipe, there would not have been a problem.

However, PVC is not recommended for the higher concentrations of sulfuric particularly if the temperature is elevated. The world's most resistant PVC is the red TROVIDUR (German) which their literature says, if I remember correctly, is OK to 96% or 98% @ r.t.

Other materials to consider might be PVDF and certainly the weldable fluorocarbons.

I would have thought that a heavy mild steel might be as good as stainless and far less expensive.

Food for thought, anyhow.

freeman newton portrait
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

A. Regarding 98% sulfuric corrosion: while carbon steel gives generally good service in storage, you can have problems if there are entrapped air bubbles, high pumping velocities, or with variation in concentration. (Shipping manifests often list an acceptable range of concentrations rather than "98.00%".) Very high corrosion may result if concentration exceeds 100% - this is not a joke, read up on sulfuric to find how 100% is defined. Impurities in the acid may also cause variations in performance.

304/316 stainlesses are borderline materials - I have seen problems, especially where mixing with water occurs.

There are various higher alloy stainlesses that have good performance in sulfuric, especially where temperatures will be limited to the range you listed. The type known variously as Alloy 20 (high Cr, Ni, with Cu and Mo additions) is very widely used for sulfuric service.

paul tibbals
Paul Tibbals, P.E.
gas & electric
San Ramon, California, USA
(My opinions are not related to nor a statement of my employer's)

A. PFTE or teflon coatings on steel might serve well:

Bjorn Larsen
Environmental -

Ed. note Dec. 2017: Sorry, apparently no longer offers such pages.

Multiple threads merged: please forgive chronology errors :-)

Q. Hi,

I want to ask what is the pipe material for Sulfuric acid service (H2SO4) 98% concentration with ambient temperature Minimum 9.0 °C and Maximum 50 °C. Note, the pipe will be used for draining purposes.

SABIC/IbnRushd - Yanbu City, Western region, KSA

A. Hi Sami!

Ah, didn't you ask about 98% sulfuric back on letter 18942?

Some of the answers are applicable to your question of today ... but to get some other ideas, suggestions, go to the archives #18489.

These pertain to strong sulfuric. But as you can imagine, I'm very partial to using the correct plastic materials ... and for your personal information, it was Canada who in the very early sixties was the first in the world to invent the successful bonded dual laminate material of PVC reinforced with fibreglass, Alcore Fabricating in Richmond Hill in Ontario ...

freeman newton portrait
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).


Monel or SS316L for 98% sulfuric acid


Subhendu Roy
- Mumbai, Maharastra, INDIA

A. Yes, as long as there are no chlorides or other halides present, which are particularly difficult to eliminate.

Guillermo Marrufo
Monterrey, NL, Mexico

simultaneous replies

A. Pure sulfuric acid does not behave like diluted sulfuric does. I do know that temperature has a very significant bearing on how aggressive it is.

James Watts
- Navarre, Florida

A. Hi Subhendu ! What Guillermo says may well be right .... but due to the highest copper content of Monel, I'd double check with Wiggin in the UK.

If, if, if you maintain that high concentration, then consider, too, ordinary mild steel. But if the concentration falls, then beware.

Regarding the fumes, sulfuric acid has a great tendency to absorb moisture ... so I would NOT use any metal but just go to PVC. See the archives # 22519 and maybe # 15290.

freeman newton portrait
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).


Q. I am using CS plug valves (RTFE-Sleeve) with SS316 Plug in 98% H2SO4.
Will it give good results in the long run?

Santosh Sawant
- France
March 7, 2008

Q. I am working in Water Treatment Plant of a power generation site in Orissa, INDIA. We are handling sulfuric Acid (98%) to lower the pH of cooling water. During erection of the storage tank and pipelines we have used PP pipes with FRP coating. Over a period of time due to continuous exposure to all weather condition we find that the pipelines are damaged.
You are requested to help us in gathering more info on pipelines & valves that are suitable for handling sulfuric Acid (98%).

With regards

Deepak Tripathy
operational engineer - Jharsuguda, Orissa, India
March 14, 2008

Q. In our of our project in India, we have used a carbon steel tank for storing 98% concentrated sulfuric acid. What is range of concentrations of H2SO4 that can be allowed to be stored? We understand that diluted H2SO4 has a faster corrosion effect on the tank material.

Pavan Meshram
Employee - Bhopal, MP, Induia
July 16, 2008

A. Limit CS to between 93 and 98 % and keep the velocity below 2 ft per second. If the storage tank sits idle, for an outage, make sure the tank has a dry gas pad. If it is not covered with dry gas, the liquid phase will absorb moisture. If you are storing 93%, the drop in concentration will end up damaging (locally) the CS tank.

Gray Holler
Chemicals - Beaumont, Texas
August 27, 2008

Q. Gentlemen I work in water treatment industry, recently we are assigned for a big projects, changing the pipe lines that are in contact with sulfuric acid, 98 % concentration; from your experience what stainless steel do you prefer to use, welded stainless or seamless? Your response is highly appreciated.

Thank you

Firas Mousa
- Riyadh, Saudi Arabia
November 21, 2009

A. For 98% H2SO4, Cast Iron works well (esp. for pumping of acid), whereas CS and SS do not. Use of mechanical seals with Alloy-20 sleeve and gland plate is recommended. However if the concentration of the acid falls even by 2-3%, corrosion sets in. Of course, Alloy 20 is the correct choice, if the cost of equipment is not a constraint.

Sudhir Kulkarni
- Pune, India
April 24, 2010

RFQ: In utility plant we are using sulfuric acid to produce demineralized water.
I have a fiberglass portion where after some time the system wash itself using water, and I had a rupture in the fiberglass with 98% H2SO4.
We are now looking for alloy 20 everywhere and no one is willing to supply us. If you know any vendor or manufacturer please let me know.

khalid alwasmi
- shaybah, saudi arabia
May 13, 2012

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

Q. Which material serves best in H2SO4 98% --
PVC, SS 304, SS 316, PTFE?

Dharmendra S Negi
- Mumbai, Maharashtra, India
June 29, 2012

Q. Are there any pipes suitable for transferring sulfuric acid concentration of 98% at 50 °C?

Abolfazl Tokhmafshan
- Abadan, Khuzestan, Iran
January 20, 2014

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
& Software

About/Contact  -  Privacy Policy  -  ©1995-2024, Pine Beach, New Jersey, USA  -  about "affil links"