Corrosion in stainless steel pipes – Tour Odeon Monte Carlo, Monaco

Monaco on the Cote d’Azur is for many the place for the rich and beautiful of this world. Who doesn’t know the pictures of the casino, the big yachts in the harbour or the Formula 1 racing cars thundering through the gorges of houses?
In Monaco there is also the Tour Odeon. This skyscraper houses the most expensive penthouse in the world. It is said to have cost more than 300 million USD and covers the top 3 floors.

Corrosion in stainless steel pipes

As is to be expected, this building is state of the art. Of course, only materials and machines of the highest quality are used. And these are also installed with great care as you can see on the pictures. All stainless steel piping and stainless steel valves. Cleanly insulated with rock wool and metal cladding. Against heat loss in hot water or to avoid condensation on the outside of the pipes.

There are 3 water and energy supply centres in the building. One in the basement, one on the 20th floor and one on the 40th floor. There are several reasons for this. On the one hand, it is not economical to pump water from the cellar 170 metres up to the top floor. 170 meters of water column correspond to 17 bar counterpressure. On the other hand, the heat loss would be too great if hot water were circulated over such a distance. In each of these central units there are pumps, hot water boilers and a classic water treatment system to supply the apartments above.
Despite the high quality of the materials used and the chemical water treatment, the stainless steel pipes have started to rust. This first manifested itself in the slightly brownish water on the washbasins. A few weeks later it also came to pitting. Almost exclusively in horizontally laid pipes. When we first visited the site, about  every 2 months a piece of stainless steel pipe had to be replaced becasue of pitting.

The rust and the pitting have disappeared

The reason for this rust, or rather corrosion, cannot be clearly determined. The Tour Odeon is redundantly supplied with water and electricity from two sides for safety reasons. The water comes from different sources. If these two waters are mixed, this mixed water can become aggressive and lead to corrosion and resulting pitting.
This seems most likely at Merus:
– Not all homes are occupied year-round.
– Thus, no water flows for weeks or months.
– Rust can form even in stainless steel pipes.
– This rust is washed out during the next use and then collects on the horizontal pipes in the energy center.
If this assumption is correct, then the rust particles on the stainless steel are the reason for the pitting in the stainless steel lines.

Or probably it is a mixture of both reasons. The aggressive mixed water sits too long in unused lines, removes ions from the stainless steel, and rust develops.

We have installed Merus rings on each of the two inlets into the house. As well as in the flow of the hot water circulation, as shown in the picture on the right.
Initially, the customer flushed the system vigorously to flush rust particles out of the system. In addition, some of the conspicuous sinks were checked regularly.

Today, the water system is free of problems caused by corrosion or pitting.

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