Anyone who designs or runs a plant handling corrosive fluids eventually faces a very practical question: will this material withstand this chemical, at this concentration, at this temperature? This chemical resistance chart for polymers brings together the substances that come up most often in our customers’ enquiries: more than 40 combinations of acids, alkalis, oxidisers, salts and solvents, rated for polypropylene (PP), PVC and PVDF at 20 °C and 60 °C, with a room-temperature comparison against PE-HD, PTFE and AISI 316 stainless steel.
The page is designed as a quick lookup tool. If you need a reasoned comparison of the three thermoplastics (molecular structure, mechanical properties, cost and selection criteria), see our guide PP vs PVC vs PVDF: choosing the right material for chemical pumps and agitators. This article focuses on the data.
Important notice. The ratings below are indicative. They are based on general technical literature and on the compatibility charts published by manufacturers of semi-finished plastics. They refer to single substances in aqueous solution, at atmospheric pressure and without significant mechanical stress. They do not replace a check on your specific application: before choosing the material for a pump, an agitator or a tank, always confirm the data with the material supplier and the equipment manufacturer.
How to read the chemical resistance chart for polymers
Each cell combines three pieces of information: the chemical, its concentration and the temperature of the fluid in contact with the material. The rating scale is deliberately simple:
- A, resistant: suitable for continuous service. Slight changes in colour or weight may occur without affecting function.
- B, limited resistance: moderate attack (swelling, loss of mechanical properties, surface oxidation). It may be acceptable for short contact, unstressed parts or a shorter service life, but needs a case-by-case assessment.
- C, not recommended: rapid or severe attack. Do not use.
- –, insufficient data: no reliable general data, or published sources disagree. Testing is required.
Concentrations are given in percent by weight, except sodium hypochlorite, which is expressed as available chlorine as on commercial data sheets. The PVC 60 °C column sits at the material’s operating limit: even where chemical resistance is good, the mechanical margin at that temperature is small. For PE-HD, PTFE and AISI 316 we only show the 20 °C value, because they are included as reference materials rather than as the main construction materials of our pumps.
Where the sources we consulted disagreed, we chose the more cautious rating. In a chart like this, erring on the side of caution costs you a more expensive material at worst; erring on the side of optimism can cost you a plant shutdown or a product leak.
Maximum operating temperatures
Temperature matters before chemical compatibility does. A material that is chemically suitable but used beyond its thermal limit deforms, loses stiffness and becomes more vulnerable to attack by the fluid. The figures below match those in our thermoplastics guide and refer to pump and agitator components in continuous service.
| Material | Max operating temperature (indicative) | Notes |
|---|---|---|
| PP (polypropylene) | 80–90 °C | Depends on grade and mechanical load; brittle below 0 °C |
| PVC (polyvinyl chloride) | 60 °C | Loses dimensional stability above 60 °C |
| PVDF (polyvinylidene fluoride) | 100–120 °C | Good dimensional stability under load at temperature |
| PE-HD (high-density polyethylene) | 60–70 °C | Less rigid than PP; good toughness at low temperature |
| PTFE | up to ~250 °C | Literature value; mainly used for gaskets and linings |
| AISI 316 | not the limiting factor | Corrosion (chlorides, reducing acids) sets the limit, not temperature |
For pumps, the real limit also depends on the design: our PMC-1 horizontal pumps with mechanical seal are rated for temperatures up to 80 °C, while the HTM magnetic drive pump, in PP or PVDF, and the VGA vertical pump go up to 90 °C.
Chemical resistance chart: inorganic acids
Mineral acids are where thermoplastics clearly outperform metals. Hydrochloric acid attacks stainless steel even when dilute, while PP, PVC and PVDF handle it well. Oxidising acids are a different story: concentrated nitric acid and chromic acid oxidise the hydrocarbon chains of PP and PE, and PVDF becomes the safer choice.
| Chemical | Conc. | PP 20 °C | PP 60 °C | PVC 20 °C | PVC 60 °C | PVDF 20 °C | PVDF 60 °C | PE-HD 20 °C | PTFE 20 °C | AISI 316 20 °C |
|---|---|---|---|---|---|---|---|---|---|---|
| Sulphuric acid | ≤ 10% | A | A | A | A | A | A | A | A | B |
| Sulphuric acid | 50% | A | A | A | B | A | A | A | A | C |
| Sulphuric acid | 96–98% | B | C | B | C | A | A | B | A | B |
| Oleum (fuming sulphuric acid) | – | C | C | C | C | C | C | C | A | – |
| Hydrochloric acid | ≤ 10% | A | A | A | A | A | A | A | A | C |
| Hydrochloric acid | 37% | A | B | A | B | A | A | A | A | C |
| Nitric acid | ≤ 10% | A | B | A | B | A | A | A | A | A |
| Nitric acid | 40% | B | C | B | C | A | B | B | A | A |
| Nitric acid | 65% | C | C | C | C | A | B | C | A | A |
| Phosphoric acid | 85% | A | A | A | B | A | A | A | A | B |
| Hydrofluoric acid | 40% | A | C | C | C | A | A | A | A | C |
| Chromic acid | ≤ 20% | B | C | B | C | A | A | B | A | B |
A few notes on these ratings:
- Concentrated sulphuric acid. At 96–98% PP tends to oxidise and darken even at room temperature; PVDF handles it at elevated temperature too. Oleum, which contains free SO3, attacks every thermoplastic in the chart.
- Hydrochloric acid 37%. PP and PVC are resistant, but concentrated HCl slowly permeates through the walls. Staining on the outer surfaces of tanks and pipes, and corrosion of nearby metal parts, are common side effects.
- Hydrofluoric acid. PE-HD is often preferred to PP for dilute solutions because it is less prone to stress cracking. PVC is not recommended. For high concentrations or temperatures above 40 °C, use PVDF.
- Chromic acid. PP and PVC are used in chrome plating baths at moderate temperature, but service life depends heavily on concentration and temperature. That variability is why we rate them B at 20 °C and C at 60 °C.
Organic acids
Organic acids are generally less aggressive than mineral acids, with one important exception: glacial acetic acid swells PVC and should be handled in PP or PVDF.
| Chemical | Conc. | PP 20 °C | PP 60 °C | PVC 20 °C | PVC 60 °C | PVDF 20 °C | PVDF 60 °C | PE-HD 20 °C | PTFE 20 °C | AISI 316 20 °C |
|---|---|---|---|---|---|---|---|---|---|---|
| Acetic acid | 10% | A | A | A | A | A | A | A | A | A |
| Glacial acetic acid | ≥ 96% | A | B | C | C | A | B | B | A | A |
| Formic acid | 85% | A | B | B | C | A | B | A | A | B |
| Citric acid | aqueous sol. | A | A | A | A | A | A | A | A | A |
| Oxalic acid | aqueous sol. | A | A | A | A | A | A | A | A | B |
Alkalis and caustic solutions
With strong alkalis the ranking between materials reverses. PP and PE-HD resist caustic soda and caustic potash at all common concentrations, including at elevated temperature. PVDF, despite being the most resistant material with acids, can discolour and crack in contact with hot concentrated alkalis. In concentrated caustic soda circuits above 50 °C, PP is more reliable than PVDF.
| Chemical | Conc. | PP 20 °C | PP 60 °C | PVC 20 °C | PVC 60 °C | PVDF 20 °C | PVDF 60 °C | PE-HD 20 °C | PTFE 20 °C | AISI 316 20 °C |
|---|---|---|---|---|---|---|---|---|---|---|
| Sodium hydroxide (caustic soda) | 10% | A | A | A | A | A | B | A | A | A |
| Sodium hydroxide (caustic soda) | 50% | A | A | A | B | B | C | A | A | A |
| Potassium hydroxide | 50% | A | A | A | B | B | C | A | A | A |
| Ammonia (aqueous solution) | 25% | A | A | B | C | A | B | A | A | A |
| Calcium hydroxide (milk of lime) | slurry | A | A | A | A | A | A | A | A | A |
Concentrated ammonia attacks PVC; aliphatic amines (not listed) also attack PVDF and should always be checked.
Salts, oxidisers and process solutions
Salt solutions are rarely a problem for thermoplastics. They are a problem for AISI 316: chlorides and ferric chloride cause pitting corrosion, even at room temperature. With oxidisers such as hypochlorite, hydrogen peroxide and chlorine, temperature and concentration decide everything.
| Chemical | Conc. | PP 20 °C | PP 60 °C | PVC 20 °C | PVC 60 °C | PVDF 20 °C | PVDF 60 °C | PE-HD 20 °C | PTFE 20 °C | AISI 316 20 °C |
|---|---|---|---|---|---|---|---|---|---|---|
| Sodium hypochlorite | ≤ 5% av. Cl | A | B | A | B | A | A | A | A | C |
| Sodium hypochlorite | 12–15% av. Cl | B | C | A | B | A | B | B | A | C |
| Hydrogen peroxide | ≤ 30% | B | C | B | C | A | B | A | A | A |
| Hydrogen peroxide | 50% | C | C | C | C | A | B | B | A | A |
| Chlorine (wet gas) | – | C | C | B | C | A | A | C | A | C |
| Ferric chloride | saturated sol. | A | A | A | A | A | A | A | A | C |
| Sodium chloride (brine) | saturated sol. | A | A | A | A | A | A | A | A | B |
| Copper / nickel sulphate | saturated sol. | A | A | A | A | A | A | A | A | A |
| Demineralised water | – | A | A | A | A | A | A | A | A | A |
- Sodium hypochlorite. PVC is the traditional material for storage and dosing. PP works well with cold, dilute solutions, but with commercial product at 12–15% available chlorine it oxidises progressively, especially when also exposed to light.
- Hydrogen peroxide. Cleanliness and the absence of metal contaminants, which catalyse decomposition, matter as much as the material. Above 30%, PVDF is the only thermoplastic in the chart with an adequate margin.
Solvents and hydrocarbons
No general rule applies to organic solvents: each chemical family has to be considered on its own. PVDF resists aromatic and chlorinated hydrocarbons very well, where PP, PE and PVC swell or dissolve, but it is attacked by ketones (acetone, MEK) and dissolves in polar aprotic solvents such as DMF and NMP, which PP tolerates.
| Chemical | Conc. | PP 20 °C | PP 60 °C | PVC 20 °C | PVC 60 °C | PVDF 20 °C | PVDF 60 °C | PE-HD 20 °C | PTFE 20 °C | AISI 316 20 °C |
|---|---|---|---|---|---|---|---|---|---|---|
| Methanol | 100% | A | A | A | B | A | A | A | A | A |
| Ethanol | 96% | A | A | A | B | A | A | A | A | A |
| Isopropanol | 100% | A | A | A | B | A | A | A | A | A |
| Acetone | 100% | B | C | C | C | C | C | B | A | A |
| Methyl ethyl ketone (MEK) | 100% | B | C | C | C | C | C | B | A | A |
| Ethyl acetate | 100% | B | C | C | C | B | C | B | A | A |
| Toluene / xylene | 100% | C | C | C | C | A | B | C | A | A |
| Dichloromethane | 100% | C | C | C | C | B | C | C | A | A |
| Trichloroethylene / perchloroethylene | 100% | C | C | C | C | A | B | C | A | A |
| Dimethylformamide (DMF) | 100% | A | B | C | C | C | C | A | A | A |
| Diesel / mineral oils | – | B | C | A | B | A | A | B | A | A |
Manufacturers’ charts are not consistent on ketones and esters: some rate PP as resistant to acetone at 20 °C, others as limited. We chose B. Rigid PVC is unsuitable for every solvent in the chart except the alcohols.
Factors that change chemical resistance
A chart summarises how a material behaves under standard conditions. In a real plant other factors come into play, and they can turn an A into a B, or a B into a C.
Concentration
Resistance does not always change linearly with concentration. Dilute sulphuric acid is mild for PP; at 98% it is an oxidiser. Check the actual concentration in service, including changes caused by evaporation or topping up.
Temperature
As a rule of thumb, every 10 °C rise noticeably speeds up chemical reactions and the diffusion of the fluid into the polymer. A material rated A at 20 °C can drop to B or C at 60 °C. Design for the maximum temperature reached, not the average: peaks during cleaning, exothermic dilution (sulphuric acid is the classic case) and heating cycles matter more than the nominal value.
Mixtures
The chart rates one chemical at a time. Mixtures can behave very differently: nitric acid combined with hydrofluoric acid, sulphuric acid with oxidisers, or an acid solution containing traces of solvent can attack a material that resists each component on its own. Mixtures need a dedicated assessment and, for critical processes, an immersion test.
Mechanical stress and stress cracking
A loaded component (a rotating impeller, a shaft, a bolted flange) is more vulnerable than an unstressed test specimen. Environmental Stress Cracking, the cracking caused by stress and fluid acting together, mainly affects polyolefins in contact with surfactants, alcohols and some oxidisers. Residual stresses in moulded parts make the problem worse; this is why the critical components of our pumps are machined from solid, as explained in our article on solid block CNC machining.
Permeation
Some small molecules, such as HCl, chlorine, bromine and certain solvents, slowly pass through polymer walls without visibly degrading them. Permeation does not necessarily damage the plastic part, but it can corrode external metal parts (bolts, frames, motors) or contaminate the fluid. Thicker walls and fluoropolymers reduce it.
Seals and elastomers
The chart covers structural materials. In a pump the weakest link is often the O-ring or the seal: a PVDF casing with an incompatible gasket will still leak. Elastomers (FKM, EPDM) and PTFE must be selected with the same care, using their own compatibility charts.
From the chart to pump and agitator selection
The chart is a first screening tool. In practice the final choice also weighs cost, availability of semi-finished stock, mechanical loads and expected service life. Some practical pointers:
- For dilute acids and alkalis at moderate temperature, PP covers most applications. It is the base material of our horizontal and vertical pumps.
- For hypochlorite and cold applications where stiffness is needed, PVC remains a sound choice.
- For concentrated acids, strong oxidisers, hydrofluoric acid and temperatures up to 100–120 °C, move to PVDF.
- For agitators, the shaft can be AISI 304-316 stainless steel or steel coated with PP, PVC, PVDF or PE-HD. With chloride-rich fluids or reducing acids, the thermoplastic coating protects the steel, as on our EVL fast mixers.
- For heating and cooling aggressive fluids we build heat exchangers in PP, PE, PVDF and PVC, as part of our special equipment range.
If your fluid is an acid, you will find guidance on pump configuration (single seal, double seal or magnetic drive) in our guide to pumps for corrosive acids. For surface treatment baths, where acids, metal salts and high temperatures coexist, see also our article on agitators for electroplating.
Frequently asked questions
What is the difference between “limited resistance” and “not recommended”?
With limited resistance (B) the material suffers moderate attack: it may swell, lose some mechanical properties or discolour. It can be acceptable for occasional contact or lightly stressed parts, but service life is shorter and must be assessed case by case. Not recommended (C) means rapid or severe attack: do not use the material under those conditions.
Is PVDF always the safest choice?
No. PVDF is the most resistant material with strong acids, oxidisers, aromatic and chlorinated hydrocarbons, but it resists hot concentrated alkalis less well than PP and is attacked by ketones, amines and solvents such as DMF and NMP. It also costs several times more than PP. Specify it when it is genuinely needed.
Can I use the chart for a mixture of chemicals?
Only as a first indication. Mixtures can be more aggressive than their individual components, for example nitric acid with hydrofluoric acid, or acids in the presence of oxidisers. A mixture needs a specific assessment and, in critical processes, an immersion test under real operating conditions.
Why does AISI 316 stainless steel rate worse than plastic with some acids?
AISI 316 relies on a passive oxide layer that holds up well in oxidising environments such as nitric acid, but is broken down by reducing acids (hydrochloric, dilute sulphuric) and by chlorides, which cause pitting. Under those conditions PP, PVC and PVDF last longer and cost less than special alloys.
How do I check compatibility for a specific application?
You need the fluid composition and concentration, minimum and maximum temperature, any suspended solids, the duty (continuous or intermittent) and the components involved. With that information the material suppliers’ charts can be cross-checked and, if the case is borderline, an immersion test carried out. Our technical department can run this check with you.
Check the material before you order
A chemical resistance chart narrows down the options quickly, but the final answer depends on the real application: fluid, concentration, temperature, mechanical loads and type of machine. In Flero (Brescia, Italy), Nuova Darimpianti designs and builds pumps and agitators in PP, PVC, PE-HD and PVDF machined from solid, with stainless steel or coated shafts, and has been helping customers choose the right material for decades.
Have a fluid to handle and not sure about the material? Contact our technical department with the chemical, concentration and temperature, and we will help you check compatibility and select the right pump or agitator.