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Pitting Corrosion

Pitting Corrosion - the origin of this hole in the pipe. If corrosion occurs in metal pipes, they are likely to leak over time. In the vernacular this is also called „pitting corrosion“, although this is not correct. Some steel is more susceptible to pitting corrosion than others. As a rule of thumb, the more impure a steel, the more likely it is to pitting.

Pitting corrosion is usually the result of galvanic corrosion. This occurs when two different metals and water come together as electrolytes. This creates charges – like in a battery, electrons flow. The electrons flow from the base metal to the noble metal. In order to prevent a cause of pitting corrosion, a piece of brass should always be installed between the iron and the copper in a mixed installation.

Pitting Corrosion animated

 

Pitting

Why and how?

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If impurities, such as iron particles, enter a system of copper tubes or stainless steel from the outside, these iron particles form many small galvanic elements with the tube material. The corrosion starts immediately. The material of the pipe is not essential, whether copper, aluminium, stainless steel or iron. The decisive factor is the potential difference between the pipe material and the foreign particle.

Here in the picture on the left we show a detailed technical version of how corrosion and pitting occurs. Explanations to each picture and partly graphically animated.

Depending on the water and the quality of the pipe, this process takes place more quickly in areas that have already been attacked than in a pipe whose surface is still intact. Over time, the pitting then eats its way through the pipe. This becomes leaky and a hole develops. This piece of pipe with the hole must either be repaired or replaced.

The damage can be quite high. Repairing the pipe is not the problem. It’s the water damage it can cause. The escaping water that is distributed in walls and floors. Frequently the search for the place in the pipe which has the pitting corrosion is extremely laborious and complex.

Preventive against pitting corrosion

The Merus Ring can be used preventively. To reduce the likelihood of pitting in the first place. Or in the best case to stop an existing acute pitting corrosion. Of course, Merus can only influence corrosion or pitting that occurs from the inside out. Merus is not suitable for preventing corrosion on the outside of the pipe.

We are not one hundred percent able to prevent pitting corrosion. The reason for this is that strong chemical forces act when different elements react. However, experience in projects implemented by Merus shows that the frequency of pipe damage has decreased by more than 90%.

In a particularly drastic case at a customer with around 100 residential properties, pipe damage had to be repaired every three to four months beforehand. After the installation of Merus 8 years ago, two more cases have occurred since then.

In addition, experience has shown that Merus is able to significantly reduce the corrosion rate in pipes and systems. Systems with a corrosion removal of 10 MPY stabilize at values +/- 1 MPY. If the total corrosion in a pipeline or system is reduced as far as possible, the probability of pitting corrosion also decreases dramatically.

In any case, it is advisable to install a dirt filter or particle filter at the water inlet of a property. This prevents foreign particles from entering the water installation from the outside.


 

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