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topic 33550

Mild Steel for 98% sulfuric acid storage tank

A discussion started in 2004 & continuing through 2017.


Q. Sir,

Can mild steel be used as material for storage tanks of sulfuric acid at 99% concentration at 38 °C?


Mechanical Engineer

Bryan Cunanan
- Ortigas, Mandaluyong, Philippines


A. Hi Bryan. Sulfuric acid at that concentration does not corrode steel. But to say that is not quite the same as to say that it is okay to build the storage tank from mild steel; there are "what ifs" to be considered by the engineer, including whether anything might allow water into the tank ... because then the solution would aggressively attack steel. Good luck!

Ted Mooney, amadeya42.com Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


A. Hi Bryan,

Have a gander in the archives #22519 and 28673 ... these may give you some insights.

What would concern me would be the chance of the 99% being reduced and THEN you most assuredly would get some corrosion so please ensure you maintain the high %!

And for venting any fumes, DON'T use steel ... it will fail ... use PVC.... thank you!

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).


A. Many years ago when I worked for NCR in Dayton. We used a mild steel tank for the bulk storage of concentrated sulfuric. I know the tank was more than twenty years old, and there was never a problem.

jeffrey holmes
Jeffrey Holmes, CEF
South Carolina


Q. Sulphuric acid tank. I'm working on a project that would utilize a sulphuric acid storage tank on the order of 5000 gallons, would Trovidur type PVC be suitable for this sort of application? Or would I be better served using steel and trying to keep the humidity level down inside the tank?

David Preston
student - Manchester, Connecticut, US


Hi David,

What you forgot to mention was 1) concentration and 2) temperature.

If 96% commercial at room temperature, the Trovidur would be OK ... but then so would the UK's DARVIC along with Simona uPVCs.

If the concentration can drop, BEWARE of using m.s. or even 316 s.s. .... it depends.

Sulphuric has a great affinity to absorb moisture and this can lead to failure.

Freeman Newton
Freeman Newton
White Rock, British Columbia, Canada


A. Just wondering I thought that aluminum was safer to be used when storing sulfuric acid as that sulfuric acid cannot react with the aluminum once a thin layer of aluminum oxide is formed?

-- just out of interest in the subject

Ryan Key
- Qualiicum Beach, BC, Canada


A. Dear friend,

98-99% sulfuric acid is not considered corrosive to mild steel at temperature below 40 deg C.

the 1st time you'll use the tank will increase the iron content of the acid for it will react on the surface at initial contact. the acid will turn to yellow or yellowish. remember to use better metal like SS316L pipes and valves or equivalent, use also good gaskets. never allow dilution in tanks to avoid leaks, don't wash tanks with water. Seal the tanks to avoid increase in humidity. 1 mm corrosion per year must be considered.

There are many other info, I think this will help you design. Consider the S.G. of H2SO4 on strength design of tank.

Have a nice day and God bless!

Elmar M Bautista
- Bulacan, Philippines

To minimize searching and offer multiple viewpoints, we've combined multiple threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.


Q. I would like to know what type of material handles 98% sulphuric acid well.

It is meant to be used as a pipe transfer from a tank to a truck. Currently, Mild Steel, 304 and 316 Stainless steels are used. But which one is better and why? I've also heard of people using plastics. Will that be suitable as well?

David Liew
engineering - Adelaide, SA, Australia


A. Hi David,

Why not use mild steel? Should be A.OK for concentrated sulphuric.

But BEWARE if there's any chance of air ingression or a diluted sulphuric .... then the sulphuric gets very aggressive as it will absorb moisture (in the air) P.D.Q..

There are many plastics, some very expensive, that will do the job.... but have a gander at PVC. After all, this is intermittent usage and the PVC is NOT affected, like steel or stainless, when the concentration drops. Go and get some corrosion resistance data and only use Sch. 80 and make VERY sure that it is well cemented......were this a local job, I'd recommend back welding after 2 or 3 days (to let the THF solvent dry out as much as poss.) Well, you could use threaded connections + PTFE tape, of course.

Freeman Newton
Freeman Newton
White Rock, British Columbia, Canada


Q. Part of the reason why ss is favoured is the understanding that ss has more resistance than mild steel, or rather the corrosion rate is much lower than mild steel and therefore a thinner pipe line can be used.

The application for this is basically a pipeline to discharge the concentrated acid into trucks via loading arms. due to the frequent use, and also the risk of collision either with truck, rooftop, loading platform and other structures nearby, steels would be preferred has they're stronger than polymers.

I am rather new to this subject and would appreciate any inputs. Again, I would like to know, is 316 or 304 better? the loading platform, loading arm will be under a covered area, so sun exposure to the top part of the pipe can be negligible.

Cacing [last name deleted for privacy by Editor]
- Adelaide, Australia


A. Corrosive attack on SS or any metal varies wildly by concentration, purity and temperature. To be able to sleep better at night, I would look into a teflon lined pipe. It was readily available, nearly idiot proof and should last much longer. The guys around it will appreciate the safety that it will provide. Yes, it costs about twice as much.

James Watts
- Navarre, Florida

December 4, 2008

Q. I have to store 98% Sulfuric acid, I have a company telling me that Carbon steel tanks will be okay and that is how they store 96%. Please give me your thoughts as I've been told to use S/S Tanks.

James Davenport
Industrial Cleaning company - Texas

December 23, 2010

Q. Hi
Is Stainless steel not a good option at normal temperature?
I wonder what can be use at higher temperature, for example up to 250 °C, especially in chemical operations?

Hasan Demir
- Turkey

February 22, 2012

A. SS316L is easily corroded even at 40 °C acid, 2 months it will leak.

Hastelloy -- best option but expensive
Cast Iron -- resists acid but not that good in battery acid; there are high grade cast irons for acid application

Mild Steel -- fine with acid if layered with acid bricks.

SS316L if lower than 35 °C acid temp.

Glass Lined is one of the best options, check the metal and glass expansion temp difference.

Hi to Motolite Acid Staff (RDQ & DLM)

Elmar Bautista
BS ChE - Quezon City, Philippines

August 25, 2012

Q. We have built a mild steel vertical tank 3,9 m dia. X 4,2 m high with domed lid. The tank was coating on inside with glass flake and installed on flat concrete plinth. This was Nov. 2011. The tank has operated from beginning Dec. 2011 until 1 July 2012 with no visible acid leakage. To use the overnight the tank started leaking acid from the bottom only. No circular or side welds have any leaks. Could it be that --
1) there is no dehumidifier or any other apparatus attached to a four inch vent pipe situated on the apex of the dome lid?
2) as leak is not visible while tank is in position on plinth, could acid which is spilled from overflow and runs down side and ingrates (lower concentration) between tank and concrete plinth (so to speak flush fitted) cause the leak when spillage is washed down with water?
Outlet does not have visible leakage on outlet pipe or valves.
Your answers to these questions plus any other possible or factual reasons will be greatly appreciated.
Regards moose

G Watt
- Cape town, South Africa

December 11, 2017

Q. Anyone with experience of bulk storage of >98% sulfuric acid in an arid desert region where day time air temperature may, on occasion, exceed 45 °C? I need 2 containers of about 12000 liter capacity each. Any advice you can give, from personal experience, will be greatly appreciated.

Fuzail Siddiqui
Consulting Geoscientist - Markham, Ontario, Canada

December 20, 2017

A. If the sulfuric acid is dry (no water), then plain mild steel will work just fine.

Ask your acid supplier.

jeffrey holmes
Jeffrey Holmes, CEF
South Carolina

December 20, 2017

thumbs up sign Jeffrey, I already asked the supplier. The sales person was unable to help, hence my query. Many thanks for your reassuring remark.

Fuzail Siddiqui [returning]
- Markham, ON, Canada

December 21, 2017

A. A chemical factory I once managed had a 3000 gallon mild steel tank to hold 66 Baumé Sulfuric Acid and we had no difficulties with the tank. We did have a small leak with a discharge "L" which we attributed to the velocity of the Sulfuric Acid leaving the tank (through gravity) removing the passive surface on the steel fitting.

Tom Rochester
Plating Systems & Technologies, Inc.
supporting advertiser
Jackson, Michigan, USA
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