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Corrosion in rubber/plastic lined pipe by H2SO4 (Sulfuric Acid)


Q. I need to build a sulphuric acid pipeline 8" ID. Which would be the best suitable material for it? What kind of liner would be suitable for a steel pipe? I need it to work for over 10 years.

Carlos Celle
- Santiago, CHILE

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A. Hola Carlos !

You say Sulphuric but don't give any concentrations ...

For commercial 96% sulphuric then PVC is the choice. It will last till the cows come home. Use Sch. 80 pipe. Very carefully cement on any moulded fittings and then, min. 24 hours later, BACKWELD !

PVC (the normal type l, grade one uPVC, not sewer pipe!) .... unlike fibreglass or stainless ... should accept all concentrations of Sulphuric to 96% but the German Trovidur is said to be OK to 98%.

There is another option IF, IF, IF you are ONLY using 96% or stronger sulphuric ... and that's to use mild steel. However, this is based on the pipeline being completely full all the time ...if you have any 'high spots' where air can accumulate, then the steel will fail (Case history Globelite Batteries in Toronto where the outlet pipe failed and inundated the roof with acid ... and when the fire brigade wetted it down or used an alkali, the resulting exothermic heat ruined the roof.

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).

Sulphuric acid pipe line liner


Q. Looking for material to built a liner for sulphuric acid, 96% concentration ,pipe line. Liner should be inserted on field by one of the normal industrial way. No less than 3000 Ft of liner in one section, would be require for economic reason. Several sections will be needed.

Osvaldo Garcia
- Santiago, CHILE


A. Hi Osvaldo,

Short-n-sweet ... please go and have a look at letter 15290, "Sulphuric Acid corrosion to stainless steel".

At least you gave me a concentration factor. Thanks. This is often NOT given.

I assume and hope that this line is buried? If not, as with all plastics, allowances have to be made for thermal expansion! From a structural viewpoint, one could armour PVC with fibreglass if at all necessary.

Freeman Newton
White Rock, British Columbia, Canada


Q. Hi,

Actually, I'm using sulfuric acid in 98% concentration. Most of the system is fabricated from rubber-lined carbon steel and I face serious corrosion in two pipe segments:
1- corrosion between two valves.
2- corrosion in the open drain.
But the whole system is Okay!

For the time being, we removed the rubber lining and replaced with 316SS stainless steel as a temporary solution. Could you explain the reasons? And from your experience, what is the best material I can use for this purpose?

- Yanbu, western region, K.Saudi Arabia


A. Hi Sami !

First off I know nothing about rubbers' corrosion resistant properties, in fact I'm amazed that that rubber could stand up to 98% sulphuric.

Re your problem, here are some ideas or thoughts.

Whereas mild steel is, I think, OK for 96% sulphuric, it ...along with stainless ... sure doesn't like being in diluted sulphuric, i.e., concentrations in the 30% to 80% range perhaps. Hence your drain is allowing 'air' which contains moisture to 'contaminate', i.e.. dilute your 98% as the sulphuric concentration gets reduced. Maybe this thinking applies to rubber, I don't know. Anyhow,use PVC.

If you checked out PVDF, I think you'd find that it is OK for 98% sulphuric albeit with temperature limitations ... certainly the even more expensive weldable fluorocarbons should excel.

Re your line between the two valves ... no idea. Are you using the same type of rubber and the SAME thickness of rubber? Is air being included? If so, see above.

Hence, if the piping between the valves is subject to flow variations, scouring, turbulence... then maybe the passive barrier is disturbed.

Long, long ago, the UK firm of I.C.I. proved that whereas Polyethylene is attacked by chlorine, if the wall thickness is heavy enough, then a passive barrier forms. In other words a super heavy 'wall' is chorine resistant. Lastly, I'm a great disbeliever. Having been 'bitten' by chemical engineers with the wrong info, I say to myself, ah, 98%? Really? Is that true? Perhaps it's only 96% ... in which case uPVC @ r.t. will be OK ... but the German Trovidur PVC people claim that their 'red' PVC is OK at 98% ... Germany after all invented PVC.

I hope that this is of some help. Cheers !

Freeman Newton
White Rock, British Columbia, Canada


A. According to Resistoflex's chemical resistance search, PVDF (Kynar) and PTFE (Teflon) may be suitable pipe liners. Polypropylene is not recommended > 85% sulfuric at 80 °C. As you didn't give the temperature, I give the search results:

Maximum Temperatures for Liner            PP              PVDF          PTFE     
Corrosive Stream                      °F   °C          °F    °C        °F    °C         
Sulfuric acid (10%)                  225  110        250   120      450   230      
Sulfuric acid (16%)                  200   95        250   120      450   230      
Sulfuric acid (30%)                  200   95        250   120      450   230      
Sulfuric acid (60%)                  200   95        250   120      450   230      
Sulfuric acid (60% -- sat. w. Cl2)    75   25        200    95      450   230      
Sulfuric acid (85%)                  175   80        200    95      450   230      
Sulfuric acid (93%)                   NR   NR        200    95      450   230      
Sulfuric acid (96%)                   NR   NR        175    80      450   230      
Sulfuric acid (98%)                   NR   NR        150    65      450   230 
Sulfuric acid (>98% fuming)           NR   NR         NR    NR      450   230    

Another source rates PVC (Type I) as B for 85-100% sulfuric at 72 °F, whereas Kynar, Teflon, Noryl, & Viton rated A's.

Ken Vlach
- Goleta, California honored Ken for his countless helpful
& well researched responses. He 'disappeared' in
2008, never answering our several inquiries about
his situation. But we believe that this is his obit
and would greatly appreciate hearing from anyone
who knew him. Thank you Ken, and rest in peace.


A. Sami,

Ken Vlach hit it on the head ... you (and MOST other inquirers) don't give all the facts, in this case the temperature! So he went to a lot of trouble giving you PVDF data (I didn't because I'm too damned lazy).

One point, however ... always double check corrosion resistance charts. Ken mentioned a 'B' rating for type l PVC (which I call uPVC) for 80% to l00% sulphuric.

For 96% sulphuric, using uPVC, you can use it till the cows come home! But welding must be good and cemented pipe joints must be welded (24 hours min. later) after being cemented. .... and Trovidur's book does show one of their PVC's being OK @ r.t. @ 98% sulphuric. Personally I have encountered 98% but 96% frequently and made up piping and holding tanks which I'd assume would last for decades.

By uPVC I mean regular PVC schedule piping NOT, NEVER, EVER drainage sewer pipe which might have better impact properties but not top chemical resistance.

Freeman Newton
White Rock, British Columbia, Canada

December 7, 2014

A. Hi,

Go for PTFE or PVC lined valves / pipes. Rubber and SS not suitable for 98% H2SO4. For storage tanks mild steel is Okay for 98% H2SO4 provided you have control on moisture -- generally the vapor is very aggressive mixed with moisture.
So always the storage tank roofs and top shell plate get corroded.

Ramasamy Varadharajan

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