Plumbing: Corrosion and Dezincification

Whether you work as a plumber or fancy yourself a handy-man, it bears to know a thing or two about some of the processes that can happen, should you accidentally put two materials together that should not be together. In this article I will tell you a bit more about two of these processes – corrosion and dezincification.

Corrosion Inside

Corrosion

When it comes to water, you have to be careful what material you use with it. Take metals as an example – if you are using two different metals in the same system, they will inevitably cause corrosion. This means that if you are using copper pipe by a galvanised water cistern (which has a coating of zinc) – corrosion will occur. When it comes to copper pipes, there will unfortunately always be a very small amount of copper that dissolves in the water, despite how careful you are to clean out any copper filings. However, it is still important to take care cleaning the pipes once any work has taken place, making sure to remove all copper filings. This is because copper filings travel and ends up being deposited on the galvanised surface of the cistern. What happens when copper and zinc are in contact is that they act as a battery. This means that tiny electrical currents are produced and that the water acts as the connection between the two elements, completing the circuit. The current produced from this causes small particles of the zinc to be dissolved and it makes the coating porous. This in turn means that the water in the cistern will come in contact with the steel underneath the coating and the steel will also start to corrode. If you come across this issue, my best advice is to replace the corroded cold water cistern to a new plastic one.

Copper Corrosion

Dezincification

Some areas of the country have chemicals that occur naturally in water and they can sometimes react to metals found in certain brass fittings. This reaction is known as dezincification and it basically dissolves the zinc found in brass, leaving it just as porous as the copper pipes mentioned above. As a result, it can cause them to disintegrate. You can avoid dezincification by using brass fittings with gunmetal inhibitors. Speak to your local water company to find out more about the water in your area and whether you will need to take any of these measures. When it comes to inaccessible concealed fittings, it is mandatory to use gunmetal or another similar resistant metal for the job.

Corrosion

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