SOPRODSYSE (Durable protection solution for buried systems)

Underground structures for the storage of fluids, waste or energy, water boreholes or the transport of fluids use corrosion sensitive elements such as drilling tubes, pipelines, steel or concrete storage cells, coated cavities. The control of their integrity over very long periods (several tens of years) is thus a major issue that conditions the cost, the risk of leaks and contamination of the living environment, and consequently societal acceptability.

In the case of underground structures, the corrosion of metallic elements depends on many parameter like the mineralogy and the fluids contained in the rock, the pressure and temperature conditions of the natural environment, the chemistry of the rock, the nature of the fluid or wastes or contained product, etc. Regarding corrosion, groundwater can exhibit a wide variety of physicochemical conditions. With the trend to work deeper and deeper for some applications, more corrosive anoxic or chloride- or sulfate-rich environment have appeared, for which the use of so-called stainless steels can be effective. However, recent studies showed that these steels do not provide a long-term protection against corrosion, especially in the presence of bacteria.

The objective of the SOPRODSYSE project is to offer a self-adapting durable protection system for low-alloyed steels over very long periods and undergoing multiple operating conditions. This protection system must be effective over long periods (several tens of years to a hundred) and have an acceptable cost compared to the use of so-called stainless steels (rich in chromium).

On a scientific point of view, the SOPRODSYSE project is based on a triplex system combining an innovative surface preparation by supercritical nitrogen flow loaded with mineral particles, a coating of a dense and thick sacrificial material produced by cold spraying and a diffusion barrier layer achieved by micro-arc oxidation conversion of the cold spray coating.

The scientific and technological issues mainly consist in ensuring the adhesion of the different thick layers, formulating a sacrificial material with the compactness and the adequate metallurgical structure and developing an adaptive diffusion layer depending on the corrosion conditions.