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Nozzles for Pre-treatment applications


Engineering Considerations - Chemical compatibility

Pre-treatment tunnels are a series of stations spraying a variety chemicals. Some chemicals like the phosphates used for anti-rust conversion coating are specifically used because they react with metals. The whole point of the phosphate spray is to cause a reaction on the surface of the metal being sprayed to form a corrosion resistant film.  Spraying phosphates through metal nozzles is thus problematic. There are metals that are resistant to the actions of phosphate but they tend to be more expensive and as pre-treatment plants run and temperatures below 100 degrees plastics like glass filled poly-propolyene tend to be more cost effective choice of material.  

Poly-propelyene, PVC, CPVC or PVDF quick change system

The Unispray quick change system is manufactured in glass filled poly-propelyene, PVC, CPVC pr PVDF. These materials give excellent chemical resistance are hard wearing and relatively inexpensive. This makes them all ideal for use in pre-treatment tunnels. Indeed the Unispray system is regarded as the market leading system worldwide in this niche segment. A table of their relative properties is given below.






Material










Temp rating










Chemical compatibility










Corrosion resistance










Strength










Cost










PVC










60oC










High










Good










Low










Low










CPVC










100oC










High










Good










Medium










Medium










Glass filled poly-propeleyne










70oC










High










Good










High










Medium










PVDF










120oC










High










Excellent










High










High











Spray Tunnel Engineering Considerations

UniSpray System Parts

Pre-treatment nozzle selection table