I see lots of pictures of people showing off their magnetic filters full of magnetite and patting themselves on the back, but fitting these filters is not addressing the problem, I also see installers banging on about the need for inhibitors and that they must be added to comply with building regulations or for warranty for the boiler, this is wrong, there is no mention that inhibitors MUST be used in the building regulations and there is no mention in the majority of manufacturers manuals that lack of inhibitor in a system will invalidate a warranty, it may mention inhibitors, but does not say they MUST be used, however manufacturers do list the pH of water they require for their boilers, and conductivity of the water in their boilers, but how many installers actually check these facts
Another point I see raised is magnetite in a system, lets just clarify something here, magnetite is the stable natural layer of iron formed to passivate the metal, inhibitors just form a false protective layer, the problem comes when these layers get disturbed and this tends to be down to poor design of the heating system, If flow rates are high, conductivity high, and the pH is low or if there is a surplus of oxygen in the system, magnetite can be disturbed on the metal surface and set free in the water
The most common reasons, are high flow rates and a high electrical conductivity, inhibitors actually increase the waters conductivity, so installers should be addressing these issues if they truly want to reduce corrosion.
I saw a blog recently from an installer commenting on electrochemical corrosion in heating systems, he called it a chemical reaction caused by the metals and water, this type of corrosion is caused between a noble (copper) and an un-noble metal iron. The inhibitor would cover the surface of these metals with an artificial layer, if it works properly this artificial layer is said to stop the electrochemical corrosion as it blocks any anodic and cathodic surface. The use of deionized water would do a similar thing. It blocks the flow of electrons due to the low electrical conductivity of the water, but with a properly designed system the electrochemical corrosion should not occur, normally you don’t fit a copper pipe directly to iron instead you have a brass piece or gunmetal between both materials, this brass piece should have a length of min the diameter of the tube to act properly as an electrical insulator, with this electrical insulation you will not have the problem of electrochemical corrosion.
We see lots of stuff in trade magazines and at trade counters telling us we need this and that gizmo to prevent heating system corrosion, where in reality we just need to consider the design of the system, check pH, get the conductivity of the water low and carry out a good de-aeration procedure these factors will reduce system corossion, rather than gimmicks which do not, it is time installers started to look more at the science of heating system water and and acting on this knowledge to prevent corrosion causing problems, not just allow themselves to be sold products they are told they need
Basically the fact of the matter is inhibitors are only necessary if the system design and the water treatment is of poor quality!