ADVICE
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CHRIS REILLY, ALTECNICS COUNTRY MANAGER FOR ROI & NI INVESTIGATES THE DESTRUCTIVE POTENTIAL OF DEZINCIFICATION AND HOW TO AVOID IT… What is dezincification?
B rass is a widely used metal alloy, made of copper and zinc. In certain circumstances, when exposed to particular combinations of pH and concentrations of chlorides, it can experience a severe form of corrosion known as dezincification. This is where the zinc dissolves out of the brass, weakening and compromising the mechanical properties of the alloy. In relation to HVAC applications, dezincification can result in system failure by causing leaks, blockages or even ruptures. It is therefore rightfully a major consideration when it comes to system design. WHEN DO I NEED TO BE CONCERNED ABOUT DEZINCIFICATION? In the UK, it is mandatory for fittings that are going underground to be dezincification resistant. Potable water is unlikely to cause dezincification, but if it is capable, or where distribution systems might introduce fluids that may cause dezincification, you should use dezincification resistant (DZR) fittings. DZR or DR brass is a type of brass used for manufacturing that gives resistance to dezincification corrosion. Products that offer dezincification-resistant properties will often be marked with the ‘DR’ mark. If you are unsure, advice can be sought from your local water authority to understand if you need to consider DZR components for your project. AVOIDING DEZINCIFICATION AT THE POINT OF MANUFACTURE Our job in this equation is to manufacture products that can offer DZR properties.
In order to produce components that can resist dezincification, we have to use the right material. Copper and bronze are
both immune to dezincification. However, both have drawbacks when it comes to manufacturing. Brass is the most practical material for high volume production, and so to offer resistance
to dezincification, we manufacture using a different grade of brass. DZR brass will typically be the CW602N, CW6265 or CW626N specification of brass rod, which has lower zinc content than standard brass rod. Traditionally, <15% zinc content has been the accepted maximum limit for avoiding dezincification. However, for stamping and machining brass we need zinc contents higher than this. Adding inhibitors to the brass allows it to have a higher zinc content, but still retain resistance to dezincification. We use DZR brass as per UK specifications which contains some arsenic (0.02 – 0.15%) and nickel (0% - 0.3%). This material will follow all normal routes of manufacture, with extra steps involved for stress relief through heat treatment. Extra care also has to be taken that there is no cross-contamination between DZR and non-DZR brass. BALL VALVES Altecnic’s WRAS approved DZR ball valves are manufactured from DZR brass
CW625N brass. DZR brass is resistant to dezincification; this is where zinc is removed from the brass due to corrosion. This means that DZR ball valves have a much-reduced risk of failing or leaking. DZR ball valves are perfect for installations under floors, behind panels etc. Ball valves manufactured using DZR are suitable for those installations where high aggressive water causes zinc leaching in the standard brass alloys and weakens the material molecular structure. “…advice can be sought from your local water authority to understand if you need to consider DZR components for your project.”
For more information, contact Chris Reilly, Country Manager for Ireland, on +353 (0)85 215 2288 or e-mail chris.reilly@altecnic.co.uk or Gary Swann, Northern Ireland Sales Manager on +44 (0)7760 596727 or e-mail gary.swann@altecnic.co.uk or visit the website at www.altecnic.co.uk
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