Body material is one of the first things specified and one of the least examined. Yet the choice affects weight, corrosion behaviour, abrasion resistance, cost and — in food and pharmaceutical duty — compliance. Here is how the common options compare and where each belongs.

Aluminium's main advantage is weight. That makes it the natural choice where the valve is mounted on a vehicle or on a structure with limited load capacity — the VT series tank truck pinch valve uses a cast aluminium body for exactly this reason, and so does the VAB flap diverter valve.

It offers adequate strength for moderate pressures and reasonable corrosion resistance in dry bulk service. It is not the material for aggressive chemical exposure or for very high pressures, and it is softer than steel where impact is a consideration.

Ductile iron — often seen on valve discs rather than bodies — combines the castability of iron with far better toughness and impact resistance than grey iron. It is a strong, economical choice for abrasive dry bulk where weight is not critical and corrosion is not severe. In our powder butterfly range it appears as a disc option for abrasive duty.

304 is the general-purpose stainless. It resists corrosion well across a wide range of media, is straightforward to weld and fabricate, and is suitable for most food and pharmaceutical applications with an appropriate surface finish. In our range, the KFB plate diverter, the KFZ plug diverter and the KFQ ball diverter are all supplied in stainless steel.

316 adds molybdenum, which substantially improves resistance to chlorides and to many aggressive chemicals. It is the standard specification for marine, chemical and pharmaceutical duty, and for any environment where pitting or crevice corrosion is a risk. It costs more than 304, so it is specified where the extra resistance is genuinely needed rather than as a default.

It is worth separating two questions that are often confused. Body material decides structural integrity and corrosion behaviour. It does not decide how the valve seals or how it resists abrasion at the sealing interface — that is a matter of seat or sleeve compound.

In a pinch valve, for example, the medium never touches the body at all, because the sleeve lines the entire flow path. Body material then becomes purely a structural and external-corrosion question, and sleeve compound becomes the material decision that governs life.

Tell us the medium, the environment and the application and we will recommend a build. Browse the full product range or read the selection guide.