Chemical Pump Material Compatibility Guide: PP, PVDF, SS 316 and When Each Wins
The four materials that cover 95% of chemical pump duty — and the honest limits of each.
Four materials of construction cover the overwhelming majority of chemical pump applications: polypropylene, PVDF, stainless steel 316, and the alloy family beyond it. Knowing what each cannot do matters more than knowing what it can.
Polypropylene (PP)
The workhorse polymer. Excellent against most acids and alkalis at practical concentrations — hydrochloric, dilute sulphuric, caustic, ferric chloride, plating baths. The limits are firm: sustained temperature above ~70 °C, strong oxidisers at concentration, and many solvents. Within its envelope, PP is the cheapest reliable answer to most corrosive duties.
PVDF
The premium polymer. Temperature capability toward 110 °C, resistance to strong oxidising acids including concentrated sulphuric and nitric, bromine, and a far wider solvent envelope than PP. The trade-off is resin cost — specify PVDF where PP genuinely cannot serve, not everywhere.
Stainless Steel 316
The right answer for solvents, food-grade duty, hot water, and high-pressure or high-temperature service beyond polymer limits. The wrong answer for hydrochloric acid, strong chlorides, and reducing acids generally — the passive film fails and pitting follows. 'Stainless' is a property of the application, not the alloy.
Alloy 20 and beyond
For concentrated sulphuric at temperature, and specific duties where both polymers and 316 fail, nickel alloys step in. Expensive, sometimes correct. Our chemical process pump range offers alloy construction where the duty demands it.
The rules that keep you out of trouble
Check compatibility at your actual temperature — resistance tables quoted at 20 °C lie about 60 °C duty. Include cleaning chemicals in the review; CIP caustic at 80 °C has killed many process-rated pumps. Remember elastomers and seal faces are part of the MOC — the best casing fails behind a wrong O-ring. And demand the Material Test Certificate: compatibility engineering is worthless if the material supplied isn't the material specified.
When in doubt, send us the liquid, concentration, temperature and specific gravity. Material confirmation against our resistance charts is part of every quotation, in writing.
Have a duty point to discuss?
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