Brass is a very popular material in valve technology and is used as a body material for valve bodies and fittings as well as for components such as sliders or plungers. Brass itself is an alloy consisting of at least 50% copper and up to around 40% zinc. Depending on the type of brass, other elements may be present that influence the properties of the brass. For example, lead as an alloying element in brass favours machinability, as it contributes to good chip breaking behaviour. The main advantage of brass over stainless steel is its price, since the machining of a brass part is faster and therefore cheaper. The advantage over plastics are the compressive strength of the material, even with thin wall thicknesses, and the possibility of integrating small threads into a brass body, which is not always possible with plastic. In contrast to aluminium, brass does not need to be additionally protected with an anodised coating, for example.
However, despite these many properties of brass, the material is not suitable for every application. In particular, its sensitivity to certain media makes the use of brass impossible in some applications. These include, for example, sulphate-containing tap water or liquids with high concentrations of chloride (e.g. salt water). The latter point applies to swimming pool applications, for example. Brass is also not suitable for use with fully deionised water.
If brass is used with such media, the alloy is often dezincified (selective corrosion). According to current knowledge, this is an oxidation process in which the copper is separated from the brass and remains behind as a porous copper sponge, while the zinc is transported off together with the medium.
Based on experience, the use of brass with such media should therefore be avoided, as should standing water in pipes, as this also contributes to dezincification.
