Ann: Re-validation of Proof of Concept , page-12

hi found this article at http://iga.igg.cnr.it/pdf/WGC/2005/2039.pdf all about embritlement in geothermal wells have included the conclusion here for a quick read
6. CONCLUSIONS
In geothermal systems, probable corrosion models should
be put forward by analyzing the system before the design
and material selection procedure. The corrosion model
should be developed under wellhead and wellbore
conditions and should include corrosion chemistry and the
effect of the fluid flow rate on erosion corrosion. Hence,
suitable material selection and corrosion control for the
design would be obtained. Although low alloy steels are
mostly preferred as easy to obtain and low in expense, the
necessary precautions should be taken in order to use them
safely in geothermal systems. The probability of stainless
steels to undergo uniform corrosion is low, when they are
used with geothermal fluids. On the other hand, some other
types of corrosion may be observed. Stainless steel material
selection and usage should be made carefully. Titanium and
titanium alloys are resistant to pit and cracking corrosions
at Cl ion concentrations below 10%. Their usage in air or
oil cooling heat exchangers is suitable. However, at high
temperatures they undergo pit corrosion. Inconel-625 and
Hastelloy C-276 are the most suitable Ni-Cr-Mo alloys for
use in high temperature geothermal fluids. Cobalt alloys are
used for applications which require resistance to abrasion
resistance and sulphur stressed compression, and high
strength. Zirconium and tantal alloys are used with channels
subjected to hot hydrochloric acid treatment. The
performance of aluminum alloys is pure because they form
galvanic and pit corrosions. The usage of concrete-polymer
mixtures which are classified as non-metallic material, and
Fiberglass Reinforced Plastic (FRP) pipes and materials,
has been rapidly increasing. The applications of Fiberglass
Reinforced Plastic (FRP) materials in central geothermal
heat systems by investors and managers are rapidly
increasing due to their high corrosion resistance, easy of
installation and short time for assembly, longer service life
and low operating costs.