• Material table of recommanded materials to be used in any design (CERN demineralized water environment). Any exception to this table shall be first approved by CERN specialists. See also this En/CV document.

Material	Demineralised Environment
	Erosion	Corrosion	Comments
Inox-316	N.A.	N.A.	Use whenever possible. L or Ti version (extra-low carbon) recommended if soldered. Considered as non-magnetic. Great care regarding Chlore pollution (close cleanning + solder action).
Copper	Critical at Vfluid > 3 m/s. (geometry and T°C dependant).	Corrosion expected. (O2 concentration).	Soft material, to be used when thermal conductivity is key factor. Discontinuities (joint, solders...) are highly critical, especially at high T°C (> 60°C). Curves shall respect minimum curvature of xx x diameter.

Recommended Material Table for water layout elements.

• Some material are particulary not compatible with CERN environment (demineralised water, several stop/restart of flow fluid, fluid velocity...). These inadequate materials can lead to critical failure after some years of operation only. ... ...

  

  Example of brass defects (crack + dezincification) leading to water leak. Complete report from A. Gerardin & S. Sgobba [CERN].

It is recommended to consider the potential difference (DDP) between metals in contact to prevent galvanic effect. Galvanic compatibility is especially a concern when using Aluminium material, in environment with high humidity. See some examples:

Copper - Aluminium:
Couple not suitable for humid environment (corrosive effect on aluminium), since total |DDP| > 0.45V.

Heat-sink and bottom Plate:	Aluminium	DDP=-0.75V
Water Pipe:	Copper (no treat.)	DDP=-0.30V
Assembly:	Cu-Al	|DDP|(Cu–Al)=0.45V

Copper* - Aluminium:
* with Sn surface treatment on copper to improve material compatibility.
Couple suitable for humid environment (low corrosive effect on aluminium, since DDP < 0.25V)..

Heat-sink and bottom Plate:	Aluminium	DDP=-0.75V
Water Pipe:	Copper + Sn treat.	DDP=-0.50V
Assembly:	Sn-Al	|DDP|(Sn–Al)=0.25V

• Reference: Compatilibité Galvanique (source: Jacques Dubois) .pdf

Erosion in copper can be highly critical. It mailny depends on:

• Discontinuities in the layout. (solder)
• Too sharp curves piping
• Temperature of the water.

Some erosion order of magnitude are given below for copper pipes, being used with demineralyzed water

• 0.1mm material loss after 30 years at 6 m/s at T°C < 50°C on straight section, without any discontinuity.
• 1.0mm material loss after 25 years at 9m/s T°C = 40°C on sections presenting some discontinuity.