Metal mesh is the traditional answer for coarse air filtration and remains the correct one in some places. Comparing it honestly with polypropylene means looking at corrosion, temperature, weight and what happens at the end of service, rather than at strength alone.
Where metal wins
Temperature, clearly. A polypropylene screen will soften well below the temperatures a stainless mesh ignores, so anything near a heat source, in a flue path or handling hot process air is metal’s territory. Metal is also stiffer, which matters for large unsupported panels.
And metal mesh can be made very fine. Where the requirement is a fine woven screen rather than a coarse one, a plastic honeycomb is not a substitute.
Where metal loses
Corrosion, in most of the environments that cause problems. Galvanised mesh rusts at a coastal intake within a couple of years; even stainless is not immune to chloride attack in the right conditions. Rust is not only a structural problem – the corrosion products become part of the loading, and a rusting screen sheds into the air stream it is supposed to be cleaning.
Weight matters more than it appears to. A large metal panel is awkward to remove, wash and refit, and awkwardness is what stops maintenance happening. A plastic panel of the same size can be handled by one person from a ladder.
Cost over the service life
Initial cost usually favours galvanised mesh. Life cost often does not, once replacement due to corrosion and the labour of handling heavy panels are counted. The honest answer depends on the environment: inland and dry, metal may well last longer; coastal or humid, plastic usually does.
Temperature limits, stated plainly
Polypropylene softens well below the temperatures that metal ignores. As a general guide it is not a material for hot air paths, for anything near a heat exchanger outlet, or for flue and extract duties where temperatures rise. Beyond a modest continuous temperature it will deform, and deformation is permanent.
If the air is hot, metal is the answer, and this is not a close call. It is worth checking the actual air temperature rather than assuming – many installations are cooler than people expect, and many are hotter.
End of life and recycling
Polypropylene is a single-polymer thermoplastic and is readily recyclable where a collection stream exists, which is a genuine advantage at end of life. Metal is recyclable too and more widely collected. The difference in practice is that a plastic panel is light enough to be worth transporting to a recycler, whereas the collection economics for a handful of corroded metal panels are often poor.
Neither is a reason to choose one over the other on performance grounds. It matters where the site reports on waste.
What about aluminium
Aluminium mesh deserves a mention because it sits between the two. It is lighter than steel, it does not rust in the way galvanised steel does, and it handles moderate temperatures. It is also more expensive than either, it still corrodes in salt air, and it is soft enough to deform in handling.
In practice aluminium tends to be chosen where weight and corrosion both matter but temperature rules out plastic – a narrow band, but a real one. Where neither applies, the choice is usually between galvanised mesh on price and polypropylene on service life.
What we can do
We supply reusable plastic honeycomb filter screens for applications where corrosion or handling rules out metal. Tell us the temperature, the environment and the panel size, and we will tell you honestly which material lasts longer in your case – including when that is metal.