More often than not, when I visit factories in Malaysia that are handling aggressive chemicals, I find them using polypropylene (PP) AODD pumps for fluids that require PVDF. The reason is always the same: PP is cheaper.
It is understandable. But cheap is not always cheaper. A PP pump running with Nitric Acid 68% or Sulphuric Acid 98% will degrade rapidly. The body cracks, leaks develop, and the pump needs early replacement. In most cases, the total cost of repeated premature failures exceeds the cost of specifying the right material from the start.
So when is PVDF the right choice — and when is it not?
What PVDF Is
PVDF stands for polyvinylidene fluoride — a semi-crystalline thermoplastic fluoropolymer. In plain terms, it is a high-performance plastic that offers significantly better chemical resistance than polypropylene, handles temperatures above 100°C, and resists abrasion better than most plastics in its class.
For chemical pumping applications, PVDF is commonly used as the pump head material for dosing pumps, the housing for thermoplastic centrifugal pumps, and the body of AODD pumps. It is available as both standard PVDF and conductive PVDF (KC designation in Fluimac Phoenix terminology) for applications requiring groundability in flammable or explosive environments.
How PVDF Compares to the Alternatives
Versus Polypropylene: PVDF handles a significantly wider range of chemicals than PP, particularly concentrated acids and strong oxidisers. It tolerates higher temperatures and resists abrasion better. The cost is higher, which makes PP the right choice when the chemical is within PP’s compatibility range. When the chemical is more aggressive, PVDF is the correct choice regardless of the price difference — because PP will not last.
Versus Stainless Steel 316: Stainless steel offers excellent chemical resistance, outstanding abrasion resistance, and mechanical strength that PVDF cannot match. For food and beverage applications where FDA compliance is required, stainless steel is the mandatory choice. However, stainless steel is heavy, which matters in mobile applications, and significantly more expensive. Where PVDF’s chemical resistance is sufficient, it offers a lighter and more cost-effective solution.
Versus Aluminium: Aluminium has the weakest chemical resistance of the common body materials. It tolerates less aggressive chemicals and is vulnerable to many of the same acids that attack PP. What aluminium offers is high abrasion resistance combined with a lower weight than stainless steel — making it suitable for outdoor use, mining environments, and applications with high solids content like sludge or latex where chemical aggressiveness is low. For aggressive chemicals, PVDF is the correct choice over aluminium.
When You Must Use PVDF
The clearest signal that PVDF is required is when the chemical is a concentrated acid or strong oxidiser that exceeds polypropylene’s chemical resistance. This includes, but is not limited to:
Nitric Acid 68%, Sulphuric Acid 98%, hydrofluoric acid, hydrobromic acid, aqua regia, bromine, chlorine dioxide, chromic acid 50%, potassium hypochlorite, potassium permanganate, sodium peroxide, sulphur chloride, trichlorethylene, aniline hydrochloride, pentane, nitrous acid, benzene, diethyl ether, and chlorine.
This list is not exhaustive. Always verify against a chemical compatibility chart for both the specific chemical and its concentration before finalising material selection.
When PP Is Fine
If the chemical is a mild acid, dilute caustic, or general-purpose chemical that falls within polypropylene’s compatibility range, PP is the right choice. It is a capable material for the majority of chemical transfer applications at a lower cost. There is no reason to specify PVDF if PP will perform adequately — the point is to match the material to the actual requirement, not to over-specify as a default.
Autoflo Technology stocks PVDF AODD pumps from the Fluimac Phoenix range and can advise on the correct body and diaphragm configuration for your chemical. Contact us at info@autoflotechnology.com.